Most of these aren't “myths” in the sense that they are both widely held and false. Most of them are simply points of contention in which there is room for debate among a relatively small pool of WWI historians and students.
1. Could the Schlieffen plan have worked?
For a start, are you talking about the plan originally conceived by Schlieffen in 1905 or the amended version put into action by Moltke in 1914? Schlieffen's concept called for vastly greater force (48.5 army corps) than was available then or later (Moltke deployed 34) and has been viewed not as a concrete plan of attack but a “what if?” exercise. It was also based originally on not having to fight in the East, though the 'Aufmarsch II' variant took a two-front war into account.
You seem to have a very mechanistic view of warfare, that certain things such as the success of the German offensive in 1914 being impossible. It's not as simple as that, as the elder Moltke knew well when he pointed out that “no plan survives contact with the enemy”.
Take his triumph, the Franco-Prussian War of 1870-71. It is often held up as an example of Prussian military efficiency (even a “genius for war”) and equally an example of French military incompetence. Surely there could only have been one result??? Yet if you look in detail at the initial battles – Spicheren, Froehschwiller, Vionville-Mars-la-Tour and Gravelotte-St Privat – you can see that in each case the Prussian/German forces came within a hairsbreadth of being defeated. Only at Sedan was the issue beyond doubt. Had any of the French generals made a single good decision during the other battles the result of the war could have been very different.
It's the same with the 1914 invasion. What would have happened if Joffre and Galleni had not recognised that the Germans had exposed their flank and organised a new French army to attack it? Or if a reluctant French had not agreed to join the offensive? No-one really knows, therefore you cannot say that the invasion plan, based as it was on Schlieffen's original concept, could not have succeeded.
The ironic thing is that in general I agree with you. I don't think that the Germans had the numbers – and yes, the logistics – to bring it off except if events had played more completely in their favour. But sometimes things work out unexpectedly, as the elder Moltke knew.
Other points...
In posts #8-10 you and @Haraldje discuss the importance of the younger Moltke transfering 2 divisions to the east in 1914. It wasn't 2 divisions, It was 2 corps – twice the numbers.
Also, I'm not sure which vote by the SPD is being referred to. More pertinently, perhaps, is that the Kaiser and Tirpitz pushed naval expansion so hard in the years up to 1912 that there was little money for the army. It was only in 1913 that Germany gave up on the naval race with Britain and started expanding its army again. If that decision had been made earlier, the Germans would not only have had more troops, but possibly there wouldn't have been a BEF to contend with in the initial battles.
Oh, and don't think I don't realise what you're doing with some of your sources. When you cite Stahel, for example, you summarise his argument well and even give page references. However, you haven't read this book; you've just lifted the info from Wiki, which is at least better than some of the videos you think are good source material!
2. If Paris was captured by the Germans, the French would surrender
A 'non-myth' to my mind. The French government had already started to move out when the situation looked bleak and was conducting business from elsewhere. The only way the fall of Paris would have prompted a final surrender would have been similar to 1871, I.e. the total defeat of French forces - plus in this case - the failure of their Russian and British allies to rescue them.
3. If Paris was captured by the Germans, the French wouldn't be able to move their armies easily
I have no opinion on or knowledge of this, but it's an example of you promoting an interesting detail of military history to the grandeur of a 'myth'.
4. If Germany had only went [sic] against the Russians, the British and French wouldn't have declared war
The French were bound by the treaty of 1892 to support Russia with all force of arms in the event of attack by Germany. So who on earth is suggesting that they wouldn't? You (or some random video author) are creating a straw man simply so you can glorify it as a myth and knock it down. That's very poor historical practice.
The British case is more complicated, but I don't see any way that Britain could have declared war in 1914 if Germany had invaded only Russia, and certainly not in August. If you forget what you call “logic” and examine what actually happened in the decision-making process in London you would see that the Cabinet was very divided about what to do in the event of war. While Asquith, Haldane and Churchill were more bellicose in general, even the latter was not convinced initially of the need to fight if the Germans “only go a little way into Belgium”. On the other hand, other senior ministers such as Morley and Simon were radically opposed to war. The decision was so much in the balance that the French ambassador was on the verge of collapse on August 1st because he feared that Britain would leave France and Russia in the lurch. The situation changed on August 2nd and some of the anti-war faction resigned from the Cabinet.
Yes, I agree that Britain's foreign policy was generally to try to prevent one power becoming dominant in Europe, but if the decision about Belgium and Britain's Entente obligations to France was so difficult there wasn't a chance in hell that the Cabinet could have declared war simply to aid Russia. Admittedly, the war would have been expanded when France in turn was drawn in, but there clearly would have been no stomach in the Cabinet to support offensive French action. Later on, perhaps the situation would have changed as Realpolitik overtook principle, but that's conjecture.
5. Focusing on the Russians was the better option
It was never seriously considered so why bring it up? Plans to strike in the east were dropped finally in 1913, but had been on the back burner for some time. France would still have been brought into the fight, was burning for revenge for 1870-71 and was a greater military threat than Russia.
6. Austria-Hungary was a tough nation
This is honestly the worst of all your examples. There wasn't a general or statesman around who thought that A-H was in the class of Germany, France, Britain or Russia. While Turkey might have been the 'sick man of Europe' A-H was widely considered to be heading to the hospital next. Even the Austrians themselves didn't regard themselves as being among the front rank of European powers, which is a) why they felt threatened by the growth of Serbia, and b) why they had to go to Germany to get what was effectively permission to punish the Serbs.
7. Had the Germans veered southwest instead of south after going through Belgium, they would've taken Paris
Meh. A myth that has kept me awake at night for decades (not). See above response to the Schlieffen Plan.
When you return to this in post #7 you appear to put up yet another a straw man. Who are the “various people” who “have claimed the Germans could still have won after 1914”? Yes, there were some dicey moments such as the French strikes in 1917 and the huge advances of the final German offensive in Spring 1918 but that's about all I can think of. Yes, I know about the Crown Prince. Moltke said virtually the same thing before he had a nervous breakdown and got shuffled off into retirement.
8. The Russians couldn't have knocked out Austria-Hungary in '14
Yet another example of a pointless straw man, presumably raised to make you (or the person who came up with this alternate history) look good. The central point is that Russian military planning was based on the alliance with the French and the need to attack Germany before that country knocked out France. What's the point in pontificating about this type of hypothetical? Why is it a 'myth' when basically no-one has even heard of the suggestion???
9. The colonies did nothing for the Germans
Ok, so maybe Lettow-Vorbeck did tie down more Allied resources than he expended but again this is hardly worth dignifying as a 'myth', is it?
10. The Hindenburg Line was exceptionally tough
The massed tank attack at Cambrai did achieve success initially and there had been inroads made earlier in the year. Ultimately Allied attacks in the area failed dismally, including a very successful German counter-attack at Cambrai. Ok, so “tough” if not “exceptionally tough”? (As most linear defences tend to be...)
11. The Battle of the Somme was just a waste of lives for the British
We're in limited agreement here, not just on the topic but the fact that it's a myth. The Somme certainly helped grind down the Germans (who had more limited manpower throughout the war) and helped relieve the pressure on Verdun. Otoh, the battle cost more Allied lives than German and didn't succeed in Haig's objective of stopping the Germans switching forces to other important areas.
12. Verdun could've succeeded
Again, I'm not sure why this is classed as a myth? Who says that victory was possible? Falkenhayn's aim was to inflict enough casualties to make France sue for peace. I agree: no chance.
13. [The] Brusilov Offensive was already a resounding success which couldn't be made too much more successful
Ok, so...? It would be a lot easier if you provided links to where you get this stuff from because they're clearly not your own ideas.