I don't think it's 100% fair to say that the Steam platform is not, or at least has previously not been healthy for the gaming industry.
While greenlight is not a perfect system, or even a good system, it and Xbox Live Arcade have exposed thousands of games and the people who made them to a huge, receptive audience. Steam is one of the biggest engines that moved the indie game market forward to become what it is now. All I buy, for the most part, are "Indie" games, from little "i" indie like Night in the Woods to the occasional "Triple I" indie like the Binding of Isaac.
Yeah, Valve is not your friend. No shit. they're a corporation and their goal is to suck you dry just like every other corporation and company. But credit where it's due, their attempts at expanding their market and profit margins inadvertently created an environment that helped indie games thrive, and also helped expand games outside of the PC space into Mac and Linux (because SteamOS is a unix based system and they require support for a lot of their games).