No, that's not really the issue to be honest. Like I said, I find that, in the skill system specifically, if you remove the dice element and simply go with player/DM narration, then the game, for me (and, yes, I'm meaning that this is for me and not a broader judgement in other people's games, specifically for me

) the game becomes ... I'm struggling to find the right word here. "Predictable" is not the right word, but, it's the closest I can come to. As a DM, if I'm narrating instead of relying on the dice, then the story becomes my story. I'm telling the players what happens. There's no surprise for me. I find that the randomization of the dice adds in that element of the unknown. "What happened?" "Well, let's roll the dice and use that to guide the answer." becomes my default approach.
Now, thinking about it a bit more, I wasn't trying to prove people wrong with my little epiphany back there, but, I worded it entirely wrong. So, let me try again.
The base definition we're working from is that
all skill checks must have a fail condition or we don't bother making the check, right? Is that a fair way of phrasing it? But, my issue is, not all checks need a fail condition. Like I said, any contest, which is a skill check, does not have a fail condition, only a win condition. You don't stop hiding because someone spotted you, you don't stop arm wrestling because someone is stronger than you and so on.
Which is why some of these examples become somewhat problematic. If there is no fail condition, then relying on a definition which requires fail conditions becomes a problem. I frankly don't see why the forgery example isn't a contest between someone's Forgery Kit Proficiency check and another character's Insight check. There is no fail condition there. You ALWAYS create a forgery. You succeeded. You made a forgery. The quality of that forgery isn't actually set in stone either. Just because you rolled poorly doesn't make it a bad forgery. After all, the other character could roll poorly as well, meaning that the forgery passed inspection.
All that means is that the forgery was good enough at this point in time. It doesn't actually tell us anything about the quality of the forgery. Just that the forgery was good enough to fool that character at that point in time. The forgery doesn't change if a second character looks at it and rolls higher and sees the forgery. Just like if two characters are observing a character using Stealth. If one character fails, and the other succeeds at their Perception check, does that mean that the Stealthing character failed or succeeded on their check? Well, the question is really nonsensical. You cannot fail a Stealth check. Your Stealth check is always a contest between your Stealth check and the other characters' Perception check(s).
((Note, it was mentioned about a character stealthing in a brightly lit empty room. That's not possible since you cannot use Stealth without something to break line of sight. It's not that the character failed a Stealth check, but rather, the character could not have made a Stealth check at all under those conditions))
Anyway, all this is rather rambling. But, my basic point is,
there are multiple tools in the DM's belt for adjudicating skill checks. There is not a one size fits all interpretation. "Checks require fail conditions" (or however you want to phrase it) is not always accurate. There are a number of checks that have no fail condition at all (opposed checks) and a number of checks where failure really doesn't have a "setback" condition (Intelligence checks to recall knowledge for example) but probably shouldn't allow for rerolls unless the in game fictional situation changes (the party finds new information, for example, resulting in addition Intelligence checks).
Use the one that best fits the situation that you are in. Dogmatic adherence to any one method will result in problems.