[MENTION=6972053]Numidius[/MENTION] - I found your long post interesting. If I've followed you properly, you're suggesting that 5e "solves" the issue of rules bloat/complexity by shifting to a very GM-driven game. To me, that seems fair, and consistent with how I generally see the game presented on these boards. (Of course that's generalising across a wide degree of individual variation.)
Thinking about action resolution, I believe there are two main ways to achieve a greater degree of symmetry at the table.
One is to go for relatively hard-coded "subjective" DCs, which then provide a reasonalby "knowable" framework for the players to exert themselves against. I look at 4e in this light; and a non-D&D system that I also think fits this description is Marvel Heroic RP/Cortex+ Heroic - though rather than a table/formula for level appropriate DCs like 4e has, it uses GM-side dice pools to generate the opposition.
Another is to go for "objective" DCs - which therefore give the GM a lot of latitude in establishing the DCs and, thereby, the "feel" of the setting (especially when, unlike 3E, GM discretion is prioritised more highly and there are fewer long lists of DCs-by-circumstance) - but to give the players (i) less reason to want to succeed all the time (eg "fail forward" techniques of resolution) and/or (ii) resources on their side that allow them to adjust upwards from their basic competence if the GM turns out to have set the DCs higher than the players hoped/planned for. Burning Wheel is a system I play and GM that has both (i) (by way of fail forward, and also because its advancement system means sometimes your PC needs to lose) and (ii).
4e also has (ii) (eg action points, healing surges, many boosting powers, etc), which combines with its use of "subjective", system-driven DCs to generate a very high degree of player capacity to respond to, engage and shape (not in meta-ways, but by rich and ambitious action declarations) the situations the GM frames the PCs into. I think for those who haven't played much 4e in accordance with this logic of the system, and whose conception of player-side RPGing comes from relatively sparse systems where the only high-octane player-side resources are spells and magic-items, it can be hard to convey the difference of play in 4e compared to those sparse systems, that results from all these player-side resources in combination with the system-driven DCs and creature builds.
Another two systems I'm currently GMing are Prince Valiant and Classic Traveller. The former has a few player-side meta-resources, but not many: players are mostly just rolling pools built from their PC stats and skills. And it uses "objective" DCs. So it relies on "fail forward"-type adjudication to encourage player-first rather than GM-driven play.
Classic Traveller also uses "objective" DCs, but - a bit like the way in which D&D spells are notionally ingame rather than meta but are able to play the role that meta resources play in other systems - the objective DCs in Classic Traveller generally happen to have a nice spread relative to the sorts of bonuses PCs have. And it also uses a lot of dice-driven stuff on the GM-side as well as the player side. This led me to make a post late last year about Classic Traveller as
a very dice-driven game. (So "negatively symmetrical", neither player nor GM driven.)