Regarding run time, I don't watch Marvel or any of that, besides Batman, but those films are easier to watch, because they are so stimulating, with special effects, rapid editing, CGI, lots of at the audience jokes. Something like The Brutalist, three and a half hours of classic style editing and writing....to me it sounds unbearable. Partially it's the subject matter, if it was a three hour take on the Sinaloa Cartel and Chino Antrax, with breathless sex and long gunfights, Mann style photography, I would be all in.
Partly it's a societies changing norms of attension span, even me, without social media, mine has probably been impacted. I still watch three hour movies in theaters, but rarely do I think they needed every minute. Mostly it's about a 30-40 min cut.
Killers of The Flower Moon
Oppenheimer
Beau Is Afraid
The Irishman (I would just never watch this again)