Another thought on Cave Slime.
Consider a system (of which some posters at least think 5e is an instance) which simply says: Cave Slime, DC 10 DEX (Acro) to avoid slipping prone when you walk on it.
How does this differ from 4e?
First, it doesn't expressly suggest that you might want to scale up your slime (from Green Cave Slime to, say, Ultra-violet Cave Slime) in encounters in more fantastic locations of the sort that higher-level PCs are more likely to engage with. Maybe there is even an implicit suggestion that higher-level PCs aren't more likely to have adventures in locations that are more fantastical.
Second, it suggests that rolling even for small chances is important. The 4e rules give the opposite suggestion: namely, don't leave DC 10 slime hanging around for parties where most of the PCs have +8 or better bonuses, but rather scale it up to slicker slime!
A further implication that might be derived from non-4e approach, in combination with 5e's bonus progression, is that it is good for the game that high level PCs have even a slight chance of slipping on bog-standard Cave Slime. There is a sense that nothing is beneath the notice of even high level PCs. Whereas 4e has a very robust sense that, as the PCs gain levels, the scale of their concerns, and of things that might trouble them, changes fundamentally.
Yeah, I agree. I think those observations are probably true to one extent or another. Obviously you can take the Vargasian approach and just not require checks for trivial Cave Slimes, but then again 5e's progression system makes it hard to HAVE really trivial checks. You have to actively fiat these things, which bothers me personally.
And in the end, it is almost certainly true that 4e produced a sort of super heroes like kind of aesthetic where high level characters really aren't much troubled by the ordinary muck and dreck of existence. The interesting thing is, in that system you can simulate the effects of luck, fate, an evil plot, whatever, by simply placing a level 20 cave slime in the path of a high level character who's 'walking down the street'. Its a sort of natural thing to do in fact. What is the fictional justification? Luck, fate, evil plot, run with it!
On the topic of contrafactual or latency: I think we can see that there are simply people who's exposure to different concepts in RPGs is not wide. I suspect that a lot of people have pretty much stuck to a few similar games that they were exposed to around the time they started playing, and the very thought of other RPG constructs is just hard for them to contemplate.
Consider AC as an example. AC in 5e is just as abstract a thing as it is in any other D&D. Most of your AC is just some sort of inherent attribute of your character, you start with 10 points of it, and even if your character is restrained (and thus certainly cannot dodge, parry, etc) you STILL have that 10 points of AC. What does it represent? It has to be much like hit points, largely luck, skill, etc. Yet there is a sort of fiction about the mechanics that says that 'plate armor is AC 16, that's a physically modeled realistic thing.' But then why isn't it 6 if you're restrained? Why, if 2/3 of that value is really some sort of abstraction is it that one would feel a requirement to have every single creature in 5e that is clad in plate armor be AC 16? I mean even in terms of the qualities of armor itself there's a huge difference between a 2mm thick 13th Century plate breastplate and a 16th Century 8mm thick high quality steel one. Its simply a convention, and IMHO its the conventionality that is desirable to some people. They want everything to conform to a pattern that is familiar. The qualities of the pattern are irrelevant, although many of them will vociferously object and attribute 'objective' qualities to AC, etc. It really has nothing to do with game design per-se in a technical sense.