Yeah, I've been thinking of changing my sig actually..
I've never argued that people haven't struggled, I'm arguing that the reason for their struggles is not that the PL is "too good" for them.
Di Maria was easily in the top 3 in the PL the first month or two, then he was injured, then there was the break in and his family didn't want to stay in England, then LVG decided to play him in 11 different positions and then he just sort of gave up. So I very much disagree that it was the quality of the league that he struggled with.
Özil did very well for Real and then struggled as you say initially in the PL, then now this season he flourished. If it was the quality of the PL that made him struggle at first then simple logic would tell us that he would always struggle with it, unless he became a much, much better player during his time at Arsenal. Which I don't think is the case.
Every player needs an acclimation period, whether you move to La Liga, PL or wherever you go. How long that period is varies of course from player to player. New team, new league, new country, new food etcetcetc it all comes into play.
I just don't think that the quality of the PL is that much better than the Bundesliga or La Liga, at least not so much better that top class players will struggle to play at their level when they get there.