If I may, as we go into what appears to be the clear endgame for C3, I think the lessons to take from the ending of C2 within the fandom are:
Do not freak out about the possibility of the campaign ending sooner than you expected nor you personally wanted
Last minute twists are not impossible, but if your enjoyment rests on a sudden reversal in the final hour you are likely to be disappointed
Just because it happened in prior campaigns doesn't mean it will happen in this one
Don't count your chickens before they fail to hatch
There will probably be one shots if it's a serious enough plot hook that we can't get to
Disappointment and anger are fine but eventually you do need to get over it
For the record, I think the particularly unpleasant responses to the ending of Campaign 2 boil down to the fact that it wasn't nearly as clearly signaled (the formal announcement was like two weeks in advance and while in retrospect it makes sense, at the time it felt very abrupt); that despite two relationships being established and a third clearly on the way people had convinced themselves that there would be some kind of last minute twist and their anger is entirely because that didn't happen even though there was literally zero sign it would; the fact that Molly didn't come back; and the general atmosphere of the world in June 2021 - I watched the finale while on my first trip to see my family in over a year and a half. I also think the ship wars for C2 were as bitter as they were because of both the strength of the party's bonds; but also the echo chambers that developed during a lengthy hiatus; and Campaign 3 does not and never has had anywhere near that level of serious ship warring.
The structure of Campaign 3 has been different in many ways from that of Campaign 2, which was different from Campaign 1 - that's not to say you can't make comparisons across campaigns, but I would not make assumptions based on the length of prior campaigns (plus, we're already in the same ballpark of number of episodes as C1, and the same level going into the BBEG combat as C2).
If your happiness rests on any of the now three current couples in Bells Hells breaking up, you are a weirdly bitter person, and you are likely to be disappointed. On the other hand, if you're already annoyed that a plot thread will be dropped, while there's like...maybe three plot hooks I can think of and every single one is related to Chetney, who I think will only survive the finale if Travis is unable to find a satisfying way to kill him off, we've had some excellent one shots post-campaign for both Vox Machina and the Mighty Nein and I don't see why this would be any different.
And as always I will never tell you that you can't dislike something, though there are things that, if you dislike them, I will think less of your judgment. But stick to expressing disappointment and anger; if you find yourself wanting to write out violent threats on the internet, you need to back away for a good long while. But certainly wait to be disappointed by a campaign that's already ended, and not pre-mad at things that haven't happened (or failed to happen) yet.