I think the issue some people have with Exp. Share comes down to the games not being very engaging outside arguably the meta. The changes GF has made have gotten rid of a lot of the tedium and inconvenience without actually making the experience more satisfying. On the contrary, for some players, making the games "easier" by practically handing players every tool necessary to succeed has had the adverse effect of making the games less satisfying. The less effort put into it, the less engaged the player is, lessening the psychological gratification of achieving something. It feels pointless to play a game that plays itself.

That's my theory. Exp. Share (now forced) isn't the only issue, it's emblematic of a general trend that some players hate. The games aren't actually easier, they just feel like more of a waste of time unless you want to rush to PvP or something.