Overrated top field

As many followers of chess world and chess experts like even some SGMs say, it's becoming more clear that possibly the top field of chess is too high in terms of rating in comparison to other strong players, giving the results. In open tournaments or in other massive evens like world cup and etc very strong or SGMs shows performance less, than expected by ELO system and losing points. Maybe even Magnus's rating will be lower than 2800 if strong players play more often with each other. Some people say one of the reasons can be that elite field is kinda isolated and plays almost only with each other by years, so their rating is stabiling, however they don't play much others to the point when statistics will get enough of data to adjust. Maybe people just plays better nowadays than before too. Maybe something different. Maybe combination of different factors. What do you guys and girls think about it?

And also btw this isn't just symbolic, it have some real consequences. Like some tournaments have invitations or qualifications based on rating. It turns out sometimes for elite players it is better not to play open tournaments to not lose rating so they will get their spot in more valuable tournaments with more prizes. In other hand, to other strong grandmasters it is harder to get to the elite world, as they pretty much don't get invitations to many good tournaments because of their rating, but to get that rating, they need to play more open tournaments, where they in a worse spot compared to elite which just plays with each other.