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.
Which is the best part of his designs, in my opinion. Klingons were too human like for my tastes in Berman era.
Spoiler My reasoning is that Sarek become somewhat penitent after what he was willing to do (in some opinions, unethically) against the Klingons in season 1. After losing Burnham, yet another wedge between him and his son, and probably not all that helpful for his relationship with Amanda, Sarek may have doubled down on a more pacifist standpoint, as a diplomat.