The problem with this argument is that first off, the GM can’t know your character sheet front-to-back because they’re not playing your character, so they probably don’t know if even a 1 will pass the DC they’ve set.

The GM should know exceptional stats of their player. Yes, I might not know some rarely relevant stat of my players, I but surely know how well the rogue stealths, how well the elf bowman arches, how well the mage spells and how hard the barbarian hits.

And even if I don't, the players can tell me the stat before a potential check.

In that case, and I keep repeating myself: don't roll.

Don't roll for things that can't fail.

They're talking the probability of failure, not the specific number on the die. If your skill bonus meets the DC, you have a 1/20 chance of failing, assuming a natural one equates to an auto-fail. If your bonus doesn't meet the DC, you have a higher chance of failing.

Isn’t that right foot easy stuff?

Sorry, don't know if I understand what you mean with that.

Why should they fail to tie a simple knot on a +5, dc5 use rope check 1 in 20 times?

Why should they roll for something as simple as tieing a simple knot? I don't make my players roll whether they manage to tie their shoes either.