hey, your sisters may be settled but it sounds like you're forgetting that they're 10yrs older than you - that's a whole decade more of life experiences they have that you don't!! it makes no sense for anyone to expect you to be at the same stage in life as they are! and regardless, we all have our own lives with our own struggles and setbacks, it wouldn't make sense to compare your life to theurs at any stage bc we all have our own timelines.
you're 20, which neans you've only been a legal 'adult' for 2 years now - why would anyone expect you to have a house, a successful career and your own family at this point? so you dropped out of uni, big deal. better you realised that your course wasn't foe you and quit now rather than sticking out something you don't enjoy/want to do anymore just to be miserable and not look like a quitter. bc as long as you come up with a plan to bounce back soon and act on it, then you're not a quitter. i get that it's hard knowing what you want to do for the rest of your life at this age, it's a lot of unfair pressure but it doesnt HAVE to be that way. there's no rule saying you cant have a career change later down the line. just take some time to rest and recover then make moves and get your shii together. and if you're completely clueless as to what you want to do think about what brings you joy that you could make money from, what you could see yourself doing without getting bored of in 5 mins, and ask your parents/sisters for advice too! it sounds like they have their lives together and care for you so im sure they'd be happy to help you get an idea of what you wanna do and how you wanna do it.
as for relationships - dont focus on them right now. 1) your own wellbeing should come first and it doesnt sound like you're necessarily in the best if headspaces right now. 2) your education comes next. and 3) who cares if you're not in a relationship? ik it can be lonely being single, especially when people around you are all taken, but it'll happen when it happens. you cant rush these things - if you do you run the risk of potentially ending up in a toxic relationship that makes you more miserable. im not gay but if you're struggling to find others who are, even just to make friends, try go to pride events/clubs etc? ask any lgbt friends you may have if they can inteoduce you to theirs? even just making lgbt friends online and then meeting up in person (pls be safe tho!)
finally, ik this was long and possibly very waffley but if nothing else, i want you to know things do get better. im close in age to you and a year ago i was in a very similar position, to the point where i was getting quite depressed and wondering if i should j give up. i didnt, and now im here and enjoying life way more. things arent perfect and sometimes i still have depressive episodes but i can honestly say my life is a lot better and i am much happier when i stay working and not dwelling on the bad stuff. i hope you realise the same too one day, just keep trying