Lack of personality, charisma, and life experience lead to a lot of this. With Oppenheimer you're referencing characters that are supposed to be physicists and others that are probably socially retarded in the first place so them being a bit stilted should be normal as they may have a bit of the 'tism, but outside of such an example there's definitely a problem both with how films are made and the actors themselves. When you think about the great actors that came before many had pretty full lives, many before becoming actors. Charles Bronson worked in a coal mine as a child, lived through The Great Depression, and fought in WW2; Lance Henricksen didn't become an actor until his 30's; Charles S. Dutton served a prison sentence then reformed himself and then became an actor, etc. Though that's not really an excuse when child actors like Ron Howard, Jody Foster, Kurt Russell, Jason Bateman, and Corey Feldman all did great as kids and teens (and the former four as adults, though Russell got to live life outside of acting for a while).
Films right now are by and large a paint by numbers product made from the corporate level down to be just another product to keep people on a streaming platform or to waste money on product loyalty. The corporate types have no idea how to make a good movie and the people that should be on the creative end (writers, directors, cinematographers, scorers) are just there to pump out the product to specification. I mean it's so bad now. You can look at a lot of sequels from yesteryear (especially the slasher films) and yeah they were there to just take advantage of the series' name and they weren't great compared to the films that created the series', but they had personality and were fun to watch. Now you watch the tenth Conjuring or Insidious spinoff and it feels like you've watched the same movie by the same director with the same actors, jumpscares, shots, and music before. People quite literally cannot even remember shit about them later the same night after watching the films.
All the "woke" aspects that people complain about is just another part of the paint by numbers product aspect of production, you have to have this and that and the other thing in every movie so they all feel the same everything feels forcefully inserted and not naturally developed. There's no imagination, no creativity, no way for a movie and its' characters to develop naturally.
I think a big problem with streaming helping to make sure there's more product than ever is that all the actors that would have never made (or at least made it outside of d-level work) it now have jobs.