Yeah, we'll never agree if your core issue is the half-level bonus. Having the half-level bonus was, IMO, one of the best features of the system, not something bad. The skill challenges came out half-baked to start with, I'll certainly grant you that, but that's not the skill system in its entirety--that's one specific, albeit important, application that got corrected.
No, they weren't.
They were.
This is a straight-up falsehood, often repeated but simply false.
This is how they were structured.
4e has plenty of fixed DCs for things.
A few.
It just also provides guidance for how to pick appropriate DCs when there isn't already a predefined one.
Then look up the AC for monsters...
Plate armor? Leather? Does not matter. Soldiers have AC dependend on monster level.
The only thing falsely assumed is that characters can't face challenges under or above their own CR. But actually using Monsters above or under was really winky as there was too much scaling in different areas (AC, to Hit, HP). So the function was not linear dependent on the level difference but cubic.
So back to skills. Yes, there were explanations that you should narrate the different DCs differently. But in the end, expectation was that your DC or AC is jist a function of your level. See skipp challenges table.
And believe me, coming from AD&D and 3e we really tried to make it work for us. But it just did not. And part of that reason is the scaling level bonus.
Unlike 3e and 5e, where levelling up actually does make you become worse, not better?
No, it does not. DCs are fixed.
If you use it correctly, this does not occur.
But to be fair: 4e seemed to work for you. 5e works for me in that regard.
For 3e, it has taken me years to understand that the idea is to not ever increase the DC.
I'd need to actually see it, but to put it bluntly, I straight-up don't believe that.
Weren't you around at that time? There were a few people who did remove that bonus and it seemed to work well. To be fair here: I did not test it back then as I had given up on the system. But those who tried it seemed to like it.
Actually my assumption is that 5e's bounded was partly inspired by those ideas. Or was it vice versa? I don't remember the exact timeline. 12 years ago...
On a sidenote: don't you believe me that that was a thing or don't you believe people who tried it and posted positive things about that? One is more rude than the other one.