This really rewrites "Journey to Babel". It wasn't so much about Starfleet, but Spock's refusal to follow in Sarek's footsteps. It really doesn't make any sense within the context of "Journey...". Designed to show that Spock and Sarek were different people with different views of the world (like many fathers and sons). Something that carried all the way through to "Unification", where we learn that Spock openly opposed Sarek on how to deal with the Cardassians.
It is problematic when trying to rewrite a fifty-plus year old story to try and cram in a character that was never there to begin with. "But Sybok!!!", they didn't try to rewrite Spock to fit him in, we already knew Spock felt himself as an outcast from episodes like "Journey..." and "Yesteryear".
In practice, the whole connection was designed to give Michael Burnham instant credibility with fandom. For me it failed, though it all is a "mileage may vary" type of situation.
With season three, the cord is being cut and hopefully Michael Burnham can stand on her own as a character.
Hmmm...I guess I never really thought of it that way. I sort of accepted it as the "behind the story / additional info you never knew" take on what happened, and I thought it worked well in that context. It made me feel like it was less Sarek just being stubborn and more like that there were some deep regrets that led to the fall-out. It didn't really change my perception of Michael...but it did change my perception of Sarek, and I thought in a way that enriched the character.
Like you said, YMMV certainly. It was, without a doubt, a risky thing to play around with and therefore can be polarizing. I actually think "Lethe" is one of my favorite S1 episodes because it was a moderate departure from the war / MU stuff, so it felt unique.
EDIT: I'm also one of those contrarians who likes Sybok too, though....so there is that.
