Rigging is hard, UE5 has some baked in models that offer a better than average result with minimal effort, but transition states are hard and takes effort and thats where most fail.
Running to walking, walking to crouching, running to crouching, jumping... jumping is a hard one as clothing and hair physics tend to get computationally expensive so they tend to skimp it and man does it show...
I think they actually just released a gigantic animation pack and sample for their new motion/animation tech. But the pack is like literally 500 animations or something that's presumably everything from walking to jerking it, I'm sure all duct taped together in this gigantic, convoluted state tree in just the AAA way that no tiny team would ever produce on their own.
Animation seems to feel like one of the things that games still pretty commonly fall short on. It always drives me crazy when you have these open world games and you're getting a quest or something and you both stand there 99% motionless and emotionless as you talk for 2 minutes. MAYBE someone will play some idle animations if you're lucky and facial animation is just a total afterthought because it isn't a main story beat.
Which I actually kind of get, but the barrier for entry with facial capture is way down and keeps coming way down. Like there's tools at this point where you're getting legitimately good results with an iPhone.
Outlaws for example was absolutely horrid on this front. I don't mean everyone has to have a blank check of a budget like Rockstar where they have everything mocapped down to a gnat's ball hair twitching, but this sucks in a lot of games and I guess it's getting increasingly egregious as the character models themselves get better and better.