I mean, it's the standard swing that everyone knew would come in the end. 15-10 years ago the premier league was the top league, always had 3-4 teams in the quarter finals, etc.. Ronaldo then left, there was a decline, Spain took over as the dominant team and have been dominant over the past 10 years because Ronaldo and Messi were there, while the premier league really struggled once Fergie retired (and the couple of years before that) and only once Pep/Mourinho/Klopp came in the prem did they start picking it up again.
It's nothing you can really argue, it's just the normal trend. Leagues go through transition phases just like clubs do.