I don't know if I'll really have anything new to add, but I guess I'll weigh in on the Yamato situation.
I had a suspicion. I mean, I really hoped not and I still pretty much thought he was gonna join at the end of Wano, but...yeah, I had a suspicion. When it comes to joining the Straw Hats it's not done until it's done.
There were, of course, tons of things indicating he would join, not least of which his explicit desire to do so. His tragic backstory, his rebellious "misfit" nature (both typical of Straw Hats) and his white color scheme, which hadn't yet been filled on the Straw Hat roster. But at the same time there were some oddities. His relatively late introduction into the arc, how truncated his backstory was, that there was no apparent "occupation" for him to fill on the crew, his limited (or nonexistent) screen time with the other Straw Hats. And, I don't know, he just seemed a bit too eager to join the Straw Hats. The whole thing had a "too good to be true" feel to it. With pretty much all Straw Hats there was some initial resistance, but Yamato was on board from the get go.
But hey, I still held out hope. After all, each Straw Hat's story is different in its own way. Hell, Jimbei himself doesn't really tick all the Straw Hat boxes, but here he is. Incidentally, I've always been indifferent about Jimbei joining, but I was really looking forward to Yamato. I guess now I know how a lot of Jimbei fans must have felt after Fishman Island. But nope, I guess all those funny feelings in the back of my brain were right. And now that Wano is over, I have no what clue what Oda was or is thinking with all this. I don't know, maybe Yamato staying on Wano is that "resistance" I mentioned earlier, but considering the whole context of everything else, it just leaves a bad taste in the mouth.
Vivi was one thing, which, granted, I knew going in she wasn't going to be a permanent member. But even reading week-to-week, I assume it must've been fairly obvious she wouldn't necessarily stay with them for good. While she did become great friends with them, her priority was always to her kingdom (kind of like Kinemon and Momo). And even if you genuinely were hoping for her to join, it was hard to be too disappointed. She still had her chance to travel with the Straw Hats and build a repertoire with them, and she had a phenomenal farewell, so she really got her chance to shine. It didn't feel at all like a cheat when she left. Yamato on the other hand feels like a blatant troll move.
I have no clue what Oda's long-term plan is with Yamato and, who knows, maybe he'll surprise us. But at this point in the story I'm getting kind of tired of being told to "wait for the payoff" or "it's gonna get good". In my experience, when people say that about a story, especially one that's gone on this long, well...it usually doesn't.