opinion here...
I mostly liked season 3, though I felt it was a bit of a mess by the end. It felt kind of directionless, what with the weird end of the world wedding and giving up on trying to save the world. I also felt some of the developments were less organic and more "hey, what if we tried THIS bit that we just pulled out of our backsides?". I felt there was no greater example of this than...and get ready, here comes the unpopular opinion...Vanya becoming Victor.
I get it. Elliot Page (the actor portraying Victor) had an epiphany and decided to live his truth, live as his authentic self. And I completely applaud that. I also understand it would've been uncomfortable for him to continue playing a character that possibly reminded him of who he was, when he was not happy with himself. But...that's kind of the point of acting. You play people unlike yourself. To me, it didn't make sense for Vanya to suddenly* decide "Hey, I'm a dude now!". It also was much more interesting to me to have a teeny, tiny woman be the Umbrella with the most dangerous power as opposed to a teeny, tiny man be the most dangerous member of the family. That being said, I did like how the rest of the family was like "OK, cool" and that was that.
* Now I *did* like Vanya's relationship with Sissy in season 2. That, to me, was totally understandable: she'd just gotten out of a disastrous relationship with a guy who was just using her to get his revenge on her family. I can see her not trusting men with her heart after that, plus they were just really sweet together. And I get that the character has always had to suppress who she/he was, what with Allison rumoring her into thinking she was ordinary and Daddy Dearest drugging her to suppress her powers. But I don't think that merited a total change of gender. If EP felt that uncomfortable continuing to play a female, I wish he would've quit the show and TPTB would've recast the role. If any show could've pulled off a character suddenly looking different, it would be TUA.
OK, I did like Luther asking Victor to be his best man for the wedding, but then again, he was really the only good choice of all the remaining people in the world (literally).
ETA--oops. I thought I'd finished the season but I only watched the first 8 episodes. Didn't realize there were 10 eps in season three.