The first comment on “Gygax and the Old School" captures my sense of the reverence for Gygax, much as I do respect his work: “One of the reasons why OD&D worked was because it didn’t”. Gygax built something that could be good, but it wasn’t inherently good; it just left enough space for you to make it good.
(Nothing but my personal metaphors past this point.)
I think of this in terms of machining tolerances. If something is too loose, its mechanisms jostle and collide, degrading the machine. If it’s tight, it binds up when any unwanted grit gets in.
People think of the perfect machine as the one where all the parts fit exactly together so everything runs identically every time, but in practice the best is often what has space for bits of sand between the gears
Players constantly inject grit into the system. As systems get tighter and/or more complex, they tolerate less human chaos. It’s a tradeoff between strong support and strong restrictions.
OD&D had relatively wide tolerances in a very simple machine. It let you add to it without breaking down, but if you didn’t add to it, it was often lacking. It was a good start, but people kept modifying it because it was often lacking. (I have only minimally played OD&D, so this is not based on a lot, more just the vibes it gives.)
AD&D started adding more rules, making a larger system, but did little to tighten the tolerances. The system bound up on itself a lot, making for an often janky play experience, but a single problem didn’t derail the whole thing, and various house rules rarely broke the system.
3e tried to solve the issues of binding up on itself by tightening the tolerances, preventing rules from conflicting. The game ran smoothly, but when its rules bound up it was harder to fix than AD&D had been, and it had such tight tolerances that expanding it caused issues.
OSR feels like an effort to move back towards those looser tolerances of OD&D, but often ends up with the same AD&D cruft that made that game bind up in play.
(I never played 4e.)
5e went back to looser tolerances and more space for people, a strong move back towards OD&D, along similar lines as OSR work, just less aggressively.