CapnZapp
Legend
When you say "It’s good that every character has saves that they actively suck at making" that sounds as if I am arguing the opposite. I am not.Yes, it does make a world of difference. IMO, that difference would be negative, not positive.
You aren’t being asked to do anything. The game has some (too few IMO) epic scenarios wherein only people with proficiency and/or an ability bonus will make a specific save.
The other way to get the desired result would be to have an extra rule in the stat block that says “you automatically fail this save if your save bonus is lower than X.”, which would be a less elegant way of doing it.
The idea of always succeeding on a nat 20 is bad as well, IMO, as is “your save is never worse than prof bonus”. Especially the second one. It’s good that every character has saves that they actively suck at making.
I also definately don’t think there should always be a 1 in 20 chance of success on a save. It’s a fine house rule for groups who like it, but I’m glad it isn’t a core rule.
You do suck at a save you only make if you roll 17 or better, so it's not like I'm saying characters should never have sucky saves.
What argument do you have for the "difference" to be negative? How can fixing the rules so you never have to make impossible saves be bad? Why do you fight for autofail-saves in the first place? There were never any good reason to introduce them, never mind keeping them.