In my opinion, the Premier League is too competitive for Antony. In La Liga, he was able to adapt quickly, and it can be said that he is starting to rediscover his best form. Therefore, leaving Manchester United seems to be a better option next season. Besides that, Ruben Amorim seems he would not mind releasing Antony permanently.
No, Antony has no problem with EPL, he has a problem with Man United. I'm sure Antony can adapt well in EPL if he gets a proper team. You must know that many players suddenly perform worse when they join Man United. Now, Antony proves his quality again after he is loaned to Real Betis. No doubt that it is the best choice to leave Man United.
It's certainly the best choice for Antony and many other payers to leave Man U, I've always said that, because Man U is the club with the problem and not most of those guys that people are accusing and abusing. Once you get to Man U, there is a high possibility that you will be reduced to ridicule, I feel for many of them there. And yes, if Antony is playing in other good EPL clubs, the guy will surely perform very well, Man U is like a glory killer and will continue to be so unless everything about the club changes. After all, these guys were bought for the skills and talent seen in them, so why the sudden failure if not Man U itself?