X2 and DOFP are mature themed contemporary superhero movies, I can't say they are better than MCU movies but I appreciate their style more as superhero films. Bryan Singer is a mixed bag for me, He disrespected Cyclops who is a far more interesting character than Wolverine, but I think his bad stereotypical assumptions about comics helped him in DOFP and X2.
Singer had already made movies about Nazis. He made Valkyrie later and made DOFP. So we can say he was an expert in knowing some important aspects of X-Men. Singer is more of an actor's director with a diverse body of work, The Russos are not.
Watching the final moments of Endgame with Avengers assembling, as much as I thought it was fun. its still the worst comic book cliche there is. I can't put it above the conflicted drama in DOFP that was the ''final battle''. There was no final battle because X-Men knows how to do drama and dramas are best when you have moral ambiguity characters like Magneto and mystique. Evil, right, wrong, neutrality are not as easily laid out as MCU movies make them out to be when its X-Men.
When I said I don't think the russos are a good fit for X-Men, I was looking beyond the trope. people actually think all what superheroes do is fight bad aliens from space or fight villains that want to destroy the universe. Although it is true, MCU can be very one dimensional and obvious about it. X-Men is good at scaling it down, making things more ambiguous and anonymous with less time to spend on big CGI moments and more time on the drama. I am not sure they will find that same luck in the MCU.
I like the concept of mutants best in the marvel universe as the bad mutants are not technically bad. The mutant situation is very complex. X-Men perhaps has the most interesting concept of marvel superheroes. X2 and DOFP just highlighted it well.