I'm frustrated by some of the cadence in this thread, namely the knee-jerk reaction of needing to defend commercial games as art. I don't feel the OP is at all suggesting these aren't artistic, or somehow lesser, only that there are some fundamental differences to the goals of a non-commercial game and a commercial one. Specifically in how certain genre conventions and accepted norms are more easily deviated from in an "artistic" game that does not have to concern itself with how much appeal it will have to a potential buyer. These are the sorts of games I primarily visit Itch for but they're not often easily found or brought to the surface in the current search systems.
I would personally appreciate having a more clear divide in the intent/context of a game's creation, as a way of more simply finding a specific type of game. I like the tag system for what it is and I've been able to find some of what I'm looking for through the artgame & experimental tags but having something as the OP describes, even if it's not necessarily an "artistic" vs "commercial" divide would enable more game creators to specify their aspirations for the art they produce. If nothing else, I think it's an idea worth considering as Itch grows and gains the attention of more developers seeking storefronts as avenues for commercial success/sustainability.