Could you give an example in 5e or pf2e where that’s not the case? Because that sounds pretty much like skill checks (basic flexible rules with common sense) and then the specific scenarios.

In my opinion, pf2e does this very well. One instance that has come up for me (in 5e) is doing a chase. With the existing rules, you can just have them run with their base speed, or have them make an athletics or acrobatics check, and that’ll work just fine (and is what I did) but isn’t particularly fun. Pathfinder includes specific rules for chase sequences (https://2e.aonprd.com/Rules.aspx?ID=1210) that is much more thought out and engaging. As a DM, you’re under no obligation to have to do these just because there’s a chase going on, if it’s spur of the moment base skill checks work in a pinch, but if it’s something I can plan for or I’m already familiar with those “rules” I can do something much more entertaining.

Rule 1: The DM describes the environment.

Rule 2: The players describe what they want to do.

Rule 3: The DM narrates the results of the adventurers actions.

The rules on how to play are pretty basic and very flexible. You can easily play an entire game or campaign not going past those three rules or needing anything more in depth than that.

Some folks like crunch. Some folks like heavy crunch, some like light crunch. Some folks just want a mushy bowl of cereal. We’re all just playing make believe. What rules you use is up to your table and what kind of crunch they want.

It really is crazy how hard new players defend 5e and pf2 when so many other games make GMing actually fun and easy.