A few of us have experience with NFL Fantasy Football where trading between teams has pretty much always been part of the game. It adds an enormous amount of interest, nuance and aggro .
About 15 years ago - maybe more - I played Fantasy League at work (https://www.fantasyleague.com/). They call themselves the original European Fantasy Football site, and trading is an option...but you have to pay a fee to join.
The main problem right now is that the American sites like ESPN are incredibly versatile and professional...while the new draft site on Fantasy Premier League is not. I think it will settle down. It's still way better than FF where everybody has Lukaku etc.