I used to watch a decent amount of European football.
I don't disagree that the referees are better in general (at the moment at least), but I do think that the moment a decision goes against us that might not normally be given in the Premier League (or English football more generally) people...
I suspect that a lack of personal investment might be factoring into your judgement of CL referees.
Which isn't to say they're not better, just that I don't think there's a golden level of referee where controversy disappears from the game.
If we're knocked out of the Europa due to a penalty...