HUH?
How on earth would the world be better if we hadn't got involved?
A comment like that really needs backing up.
It is difficult to create a whole centuries worth of alternative history on the basis of changing a single incident.
(the Longer the tree grows, the more branches you get!)
But the first decade or so is probably reasonably predictable.
Had we kept out of it in 1914 it is likely that the War
really would have been over by Christmas.
Treaty's would have been made and a few lines on the map would have been moved and everybody would have got to go home.
Our involvement introduced just sufficient balance to generate a bloody and pointless stalemate and great hardship for millions of people.
A rapid defeat would have been humiliating for the Russians, but it is possible that there might well have been no Russian Revolution in 1917.
The devastating economic consequences of Germanys defeat (Well, Surrender anyway) in 1918 sewed the seeds for the rise of the Nazi party and WW2.
And so on....!
Whether the flow of the river of history would have led to other reasons for global conflict throughout the 20th century, I really do not know.
The longer we look into the future past the vaguer and less firm the predictions can be.
But considering alternative histories is always fun.
I would like to think that a British Empire, not bankrupted by two massive conflicts in quick succession, might have endured for at least another century and might have had a softer landing with the ex colonies (Particularly in Africa) now being more like India* or even Canada/Australia today.
(* India is far from perfect, but had there never been a British India then todays India would probably be more like Africa, Lots of little poor countries rather than one big one that, despite its problems, is actually doing quite well)