So while it may not be fundamentally broken, it's the type of stuff that would annoy me a lot if I used an iPhone. I never expect to go from a smooth experience to a low-end Android phone experience after a software update.
MacOS... I've avoided upgrading my M4 Max MBP so far after upgrading the M1 Air we have at home. It's just not as smooth as before, even with reduced transparency.
My M4 Air has been fine after the 26 update. I haven’t noticed any difference in responsiveness.