any monster can be given more spell resistance, more hitpoints, and higher saves. boom high level monster. I think the current trend of people wanting rules to fix everything and GM to just be a referee kill GM creativity.
Sure, and that's fine.
But, for me, I like high level play to actually be different.
I don't always want orc but bigger and better. Hill giant but tougher and better etc.
For high level play to be fun (for me) the stakes have to be higher and the challenges something that just were not a thing in the lower levels.
It's one reason the early pathfinder modules rang hollow for me (maybe the latter fixed this?). Higher levels were basically the same adventures/challenges as the lower levels but with the numbers increased.