What makes an RPG good?

[Man_Over_Game]

I'm doubtful of that, though it might depends on what you call "complexity".

A lot of peoples like the depth that complexity allows.
But I don't know anybody who would prefer a D&D in which every ability score is a multiple of 0.73 instead of an integer [and the modifier associated is ((N*1.37)-10)/2, rounded down, so same game balance] just for the sake of complexity.

Complexity is the cost of interesting features of a game, but it's still a cost and you don't want to overpay.

We want a simple foundation that has no upper ceiling on the possible (optional) complexity that's available.

For example, rolling a die to see if you succeed has a very low ceiling.

Having a pool of d6s to represent your actions, and you can spend as many as you want on a single action and you can't do any action more than once, has a relatively high ceiling despite a fairly low floor.