I haven't seen the show but I know exactly what you're talking about, which is I guess the problem!!
This kind of crystallized for me why Marvel movies don't really feel like movies to me anymore, which makes sense given that they're almost as much serialized storytelling as TV. There was a specific point at which I realized I never wanted to watch another one; I was at work listening to my coworkers talk about how excited they were for Avengers: Endgame and it struck me that in 15 minutes of conversation I had not heard a single thing about plot or characterization. It was all stakes. These are cool people who I know enjoy good storytelling, so this isn't me shitting on their taste or anything, but I remember sitting there thinking, "This is literally a dead pool. The only thing I've heard people discuss about this movie is who is going to die and who's going to be a shattered shell of a person at the end of it and whether or not they, personally, think they're going to be emotionally devastated when they walk out of the theater." And I could not think of anything more exhausting than just...knowing there has to be a set threshold of main characters meeting horrible ends and laying bets on whether it'll be your favorite.
I have a theory that it's a catharsis thing, but when everything has to be aimed at meeting those ends and there are points along the line where the audience is primed to expect absolute despair, the easiest way to fuck things up without making an overwhelmingly powerful enemy is to have your protagonists self-sabotage. After being in brainstorming sessions with people who are partially responsible for setting story direction but don't have a lot of experience writing characters, it startled me how many of the suggestions that came up were basically, "What if these two characters decided they hate each other over a misunderstanding and develop a death grudge?" (The characters were friends.) "What if this other character decides to go around the protagonist and do something that seems messed up but is actually for the greater good, so everyone thinks they're evil?" (The character had just gotten through an arc about learning why doing that is bad.)
When I dug into that--because it was actually kind of upsetting to listen to as someone who did not have any input on the direction of the story myself--it seemed to circle back to most people knowing that Stories Are Driven By Conflict, but thinking of that purely in terms of interpersonal conflict. And if you've set up your primary antagonist as an apocalypse engine--because of course they are, those are the stakes--there's only so much you can do with them emotionally because there's no question that the good guys are going to murderize them in an epic battle. So the characters you actually have reasons to spend time with are your lower-stakes antagonists, more or less. They're the ones who can make each other's lives hell and thwart one another's goals without necessarily needing to kill each other.
And when they're supposed to be working toward the same goals, that frequently means the only thing they're allowed to do is act like fucking children. Saying it's like they're all 20 is spot on; I remember being that age and not realizing yet that it was okay to just. Not maintain friendships with people I had nothing in common with beyond sharing interests and I see a lot of people in that age group going through that same thing, where they either superficially align with the people in their social group in every way or they secretly hate each other.
People having nothing in common to bind them can be interesting in a situation where the stakes are so high that they're forced to put their differences aside, but in stuff like this they don't. Most mature adults who have faced any kind of real, complex problem know what it looks like when competent people with no other reason to interact button their pants up and do what needs to be done, and it's interesting! There is real tension in watching people with perfectly reasonable conflicting needs resolve things to the best of their ability. People don't have to hate each other or to have emotionally harmed each other to be in conflict, and if I can believe that the characters of your Media Property are also prioritizing the fandom slapfight that's about to occur after the episode ends, I don't care.
My favorite Star Trek novel is Uhura's Song by Janet Kagan. It was important to me as a little kid in large part because all the characters who are supposed to be adults with grave responsibilities and who care about each other act like it, and I found that really comforting. The closest thing it has to a villain is someone in a position of power who thinks they're doing the right thing, and as a result they thwart efforts to find important information by leaning on ritual technicalities in a stubborn, petty way. And what shames them is realizing that they failed a practical test of maturity that actual adolescents rose to. That's something that can be devastating to admit--especially with lives at stake--but only works if half your cast aren't pulling the same bullshit and getting away with it.
