Recalling Knowledge is a basic task, particularly about monsters. The game is set up to make knowledge about creature strengths and weaknesses super important, so you can cast spells that target their weak saves, and avoid resistances and exploit weaknesses. So someone's going to be making checks almost every combat, and those checks are spread out over 5+ skills. That can't be a specialist task.
Repairing things is also something you'll be doing after each combat, at least if anyone's using a shield to block. That's a basic task, not a specialist task.
Finding magic items and identifying them is something you do all the time, and those items will more or less scale with your own level. That can't be a specialist task either, because you're supposed to do a lot of it. This is somewhat easier because most (but not all) items can be IDed with any magic-associated skill, and you're likely to have someone who's good at at least one of them, but still.
Yes, those tasks are done all the time, but
the level they are done at are not always the same. Not every task at 20th-level should have a 20th-level DC because, as the scaling goes, they are meant to be difficult for people who didn't put some level of investment into those skills. That's
the point: checks
at-level when you start to get closer to the leveling end game become difficult because they become a smaller and smaller sliver of what can be done. Most checks at that level shouldn't be 20th unless they are going to require a specialist, which makes sense: at a certain point there should be a requirement for investment in something, rather than being able to continue to stay at the same relative level for the entire game.
Lingering composition is a spell every Maestro bard knows. Being able to use that spell properly is not a specialist task.
The Bard gimmick is based around Performance and you get ample upgrades to get to that level. I would argue that you should get automatic upgrades over time simply because they made it important to the class, but I don't think this makes the argument you want it to.
Hazards use DCs that are even higher than the normal level-based DCs – 48 to 51 is the recommended DC to disable a level 20 hazard.
Yes, it's almost like disabling a 20th-level trap rather than destroying it or avoiding it is particularly difficult. That feels like part of the point. As for non-trap hazards, a lot of them allow for alternative ways of going about them.
A superior lock is item level 17 and has a level 20 DC, and requires six successes.
Yeah, the last level of lock is particularly tough and requires you to be a specialist to have a consistent chance at success? I don't see the problem. With one choice made at the beginning of the game you can consistently pick all but the toughest locks by the end of the game feels like an incredible power given that some people will have trouble picking
any lock.
Really, why should someone who is merely
Trained, not an
Expert or a
Master be able to handle the highest level of lock consistently?
Stealing an object uses the target's (and any onlookers) Perception DC which would be 43 on average for a level 20 creature. If both stealing things, picking locks, and disabling traps are super-specialist tasks, what is a "normal" task for Thievery you'd be doing at level 20?
Yes, stealing things from level 20 creatures is damn difficult without getting noticed. Most of those creatures are meant to take on a
party of 20th level characters, hence why their stats make it that tough.
The bigger point would be "how often do I need to make a 20th-level thievery check on a 20th-level monster?" The answer should be "rarely", since doing such a risky maneuver should be suitably dangerous.
Again, we're talking about a skill with minimal investment. You can still loot 99% of the population without a problem. But as you level up, yes, these checks are meant more and more to be for people who are pouring resources into those skills, and thus they balance them about making it a challenge for them and not for the person who took it at 1st level and never did anything else with the skill. And that works out well, because as time goes on, those max-level skill checks should become rarer and rarer, since pickpocketing balors shouldn't be the standard for the kind of check you make all the time, even at 20th level. Those are spotlight skill checks for specialists, not meant for just anyone to take.
And again, there's
still the possibility (however low) that you can pull that sort of thing off. With a few bonuses and some planning, maybe you
can! But if you aren't putting some resources into those skills... yeah, you'll find yourself falling behind at the higher levels. But tunnel-visioning on just those high-level checks misses how much you can do with a low-level investment over time. Heck, just take Assurance and you'll be getting an automatic 32, which means you'll be able to always pull off Master-level tasks without fail. That's impressive on its own.