Good subtext, for me, is what separates the SimCitys and the FarmVilles. It's what makes Spec Ops: The Line work, and the Battlefield single player campaigns (to take one example) fall flat.
For me, a good mechanics-driven game is a piece of beauty, the hours I sunk into Tetris and 2048 attest to that. But, at the end of the day, these games only reward you based on simple, mechanical terms. You either grasp their mechanics and find out how to manipulate them well, or you don't. They do not invite discussions about us as gamers, they do not offer points of self-reflection or points of contention that we can debate over.