The War was a catastrophe, and amongst other things was the point at which this country stopped being a creditor and became a debtor. We went from being perhaps the wealthiest country in the world to a power on the decline.
Without British intervention the war would have likely been a very short conflict. France and Russia would have lost some prestige, a few thousand men and the Balkans would have fallen under Austrian/Germanic control.
Our intervention created one of the most violent, bloodiest and most pointless wars the world has ever seen. We funded the French and Italian war machine at great cost which ultimately led to reliance on the USA. It meant the war did not finish quickly and the Bolsheviks overthrew the Tsar in Russia, creating a terrifying state that would be at the forefront of world politics for a hundred years.
British intervention and the treaty of Versailles led to World War II (which we also effectively made a hundred times bloodier), millions of deaths and the ultimate demise of the British Empire.
As for what the world would look like today, we will never know. I'm not even going to try and guess.