Hmm.. well idk. I guess I just saw things differently, in such a way that has me feeling like.. I see the issues you guys are presenting, they are very real, very valid things to point out and pick apart but at the same time, these are points that I'd have try hard to actually see in the film and then be like "I guess you can look at it that way, but how'd you get the idea that this is where it was going??" It's like you guys were seeing something completely different from what I saw, like it's wildly different points of view.
Like the ending, for example, I didn't see it as toxic in the slightest. It has the potential to go bad sure, but for now, I see it as.. Spinel just went through a bunch of development. She's aware enough now to know when she's being used wrongfully. She's learned her lesson on being over-dependent and it was implied when she was accusing Steven of this in the climax. Towards the end, the film was briefly suggesting that Spinel was gonna go off on her own and try to find new friends, because she recognized how toxic she was to Steven and his friends in the time she was there. Fair enough, right?
And on the other side, the Diamonds are just bored on Homeworld, so bored that they'd consider moving to Earth just to stick around with Steven's quirkiness and he happens to be the remnants of Pink, who they very clearly still miss. Steven then reintroduces Spinel to them and then they offer to take her in since her and Pink have similar vibes. This is a terrible reason to take her in, but uh.. that's kind of expected of them. Steven realizes this might not be the best deal and even asks if Spinel's sure she wants to go through with it and tells her that they're not easy to get along with. But she goes anyways, because she already said she needed a fresh start.
I felt like it was the perfect solution for the moment, you know, the way the film was intending to present it in the first place lol
I didn't see as either side being "You're not Pink, but you're close enough as a replacement!" Spinel's made for entertainment, the Diamonds need it.. why not take her in? Spinel wants a new start with new friends, the Diamonds forgot about her and have no knowledge of her wrongdoings.. that's a clean slate right there. Spinel misses Pink Diamond, the Diamonds miss Pink Diamond, the opportunity to move on and form bonds is there for both parties.
Would I have preferred that the film go into a better message suggesting that Spinel should learn to be independent and love herself? Absolutely, but I'm fine with a second best idea too lol the idea that she needs to re-establish how friendships work and that it can't be one side giving everything especially after said friendship falls apart.
She knew Pink wanted a colony and Pink clearly didn't wanna bring her along once she got one. She could've backed off and offered Pink to stay friends if she left.. Pink's screwed up, yeah, but I do think she'd take that offer. Or maybe Pink could've suggested that she felt like she was growing up and told Spinel that she wasn't in the mood for fun and games anymore, but that she's moving on and told Spinel that she lived up to her purpose.. which would be far better than just abandoning her lol there's ways to make it better but yeah, the film's ending isn't that bad to me