"the tendency of this fandom to only engage with what THEY want these characters to be#as opposed to what their creators are trying to do and the stories they want to tell" slap this on a bumper sticker, you just summed all cr discourse (about PCs at least) in 2 sentences

It truly is maddening (and it's not by any means exclusive to the CR fandom). The reason why the discourse always goes the way it does is that at the end of the day, the loud fanwanky people only see what they would do, if they were self-inserted into the story, as a valid choice; and they are, more broadly, fundamentally disinterested in what others think or feel. There are several examples of this, and the variety of spaces within the fandom that produce these ideas is an indicator that this isn't endemic to one specific group of people.

-Keyleth is an important character whose feelings and choices are validated by the other PCs and cast even if they still disagree with them, in spite of how she and her preachiness get in the way of the Murderhobo Jubilee? It's not because the cast are all friends and they genuinely believe Keyleth is valid and are interested in how these discussions and choices can guide the story. It's because Marisha is the DM's girlfriend, and also here's my totally unbiased theory that my pet favorite players Sam and Travis secretly hate Marisha and Keyleth.

-Vax's presence is still felt and nodded to in the post-canon VM oneshots? It's not because he was an important character who mattered. It's because Liam wants to make everyone talk about his tragedy because he has Main Character Syndrome. Scanlan Wishes for Vax to appear at the wedding? It's not because he cares about Vex or because Sam and Liam wanted a sweet tribute to Vex and Vax's relationship and by extension Liam and Laura's friendship. It's because Liam thinks Vex's life should always revolve around Vax, and Sam wants to enable him and jerk himself off as the one who facilitated it.

-Beauyasha and Fjorester become canon? It's not because the players wanted it and it happened naturally. It's because there was a secret behind-the-scenes push to "force" those ships to become canon instead, and like, Dani Carr is some sort of shipping puppetmaster who made the players do it, and "they" (whomever "they" is) decided to sink Beaujester or Widojest because it was "obviously" going to become canon before the pandemic hiatus gave them time to "make the corporate-approved ships happen".

-Beau and Caleb try to reform the Empire and dismantle the Cerberus Assembly from within? It's not because it makes sense for their stories or that people who would take this position regarding a corrupt government might have a valid perspective that differs from your own. It's because the people at Critical Role Productions LLC are all spineless neoliberal cowards who won't commit to real activism. The best activism, after all, is violent, and violent revolutions have always resulted in stable aftermaths, and the real world has never demonstrated that this mindset is foolish.

-Relatedly: Caleb doesn't kill Trent personally? It's not because the most poetic justice would be to deny Trent the thing he wants most from Caleb. It's because "Limo Brain" is too obsessed with tragedy to have the stones to do "what needs to be done".

-Asmodeus, DnD Satan, turns out to also be CR Satan? It's not because it fits with the cosmology and the lore; it's because Matt Mercer is too attached to the "establishment", and the Prime Deities should have actually turned out to be the bad guys because of my personal baggage about Western religion and Christianity they're a little mean to my blorbo sometimes.

There's a pattern here: fans had expectations that they'd built up for themselves after projecting and building up fanon and deciding what players meant before they explained themselves fully, and when the players strayed from that, they were derided for all manner of reasons. I think we're seeing that same pattern play out in C3 as the story progresses in a way that fans dislike, and in fact we have seen fanwank spread whenever someone does anything that interferes with personally catering to a) the favored ship and/or b) the favored philosophy. (Orym, Ashton, FCG, Percy, Pelor...all valid when they affirm the Fandom Opinions and all disdained when they don't.)

Don't get me wrong, I think there's a place for comfort stories that deliver a personal catharsis. And I'm not going to dismissively say "well if you want it so bad make your own" because, as an artist, I am very familiar with the fact that creating is hard and draining and sometimes you just need to consume instead. But when you become so wrapped up in yourself and your feelings to the point where your perspective is the only valid one, someone else's feels like a betrayal when it isn't. It's always "They aren't doing what we wanted and here's why they're terrible people because of it" and never "Hmm, why is this what the cast wants? Let's examine that."

This isn't a new phenomenon, but I think it ultimately stems from not assuming that other people can differ from you in major ways in good faith. There are a lot of reasons for that (some more understandable than others), but I think you rob yourself of the potential to enjoy something new when all you do is demand what you already want. No matter what you're doing or where you are in life, you tend to become a better and wiser person when you open your mind to what other people have to say, no matter how mundane the subject matter. Sometimes the stories people have to tell are challenging—and the only healthy way to deal with that is to engage with them on their own terms.