Also, I remember a while back they did a specific optimised speed-up release of iOS with barely any new features and it _really_ worked. My iPhone 6S went from being basically garbage I was going to replace to like a brand new phone.
They can do it if they want to. It’s what’s needed now. My iPhone 12 Pro has started to feel super slow since I got iOS 17. I have a new battery. Even texting feels painfully slow. There’s no excuse for this. It’s either deliberate and bad, or lazy and bad. Either way it’s bad.
But that's a lot of maintenance burden, in exchange for slitting their own revenue throat. So hard to expect them to do it for altruism.
Sounds like you might have some buggy / bad app interactions going on? There’s really no reason for a 12 Pro to be slow at this point even if the OS was getting “heavier.” The 12 Pros have 6GB of RAM, which is now pretty standard across the iPhone lineup even years later. And the A14 SoC in the 12 Pro is effectively the same tech as the M1 processors that are still rock-solid at running full blown macOS, albeit with fewer cores running at somewhat lower clocks.
I can’t really think of much reason for you to be having a slow experience aside from the usual bugs that can accompany any new major release, and usually get ironed out over the course of a month or two.
FWIW you also don’t have to update. Of course they bully you to update. You don’t have to.
Also, ios 17 likely is a bit buggy - I’m on 17.1 beta with a 12 pro max and I can say that the performance is back to how it used to be.