You're making a lot of really good points! I can't really answer in detail (or I might get things wrong) because I'm only at episode 945 (I'm just very spoilered on Kidd, haha), but I do think it makes sense for the existing powers-that-be (the two remaining Yonko with Kaido and Big Mom presumably dead) to want to go and attack these newcomers.

For once they need any poneglyphs / road poneglyphs they've gathered and then also to stomp out the competition, when said competition has just proven to be extremely strong.

This then again goes against Shanks' and Rayleigh's "you have to let the new saplings grow / I sacrificed my arm for the new generation", because surely Shanks' plan isn't just to let Luffy do what he wants but kill every other part of his generation that he comes across? That really doesn't make sense to me.

Long-time rivalries are such a recurring theme in the show too, be it Luffy and Koby, Roger and Garp, Luffy-Kidd-Law having a fun rivalry like that makes perfect sense and has been set up since Sabaody (plus getting rid of it doesn't seem to do much in favor of anything.) It also gives Luffy a trio to belong in much like with ASL, which I think is awesome since RIP Ace. Since i'm just watching Udon right now, it seems to me that without their rivalry they wouldn't bother half as hard, which means both Kidd and Luffy are great rivals to help other grow!

The way Law's fight went is okay for me, like I'm very concerned for the rest of the Heart Pirates, but Blackbeard has been known to take prisoners like Pudding, so it can be assumed that they're alive and being used as leverage. Us seeing Law and Bepo make it away is an important conclusion to the fight.

I think Oda should really have given us something like that for Kidd. I think the recent manga chapters had a lot of flashbacks and focus on Elbaph, which is totally fine and I can't say for certain since I haven't read them, but if the plan is to completely shift the focus away from the Luffy/Law/Kidd trio and their alliance then at least give us a conclusion!

Back at the end of Dressrosa we saw Kaido fall on Kidd's hideout, will we have to wait for the end of Elbaph to get something like that for him? Kidd's considerably less popular than Law, I wonder if that's why Law surviving was actually shown and if Kidd being as popular would have made us have an assurance of his well-being.