it's a weird thing. i personally remember when valve took a far more curatorial stance in what made it through to steam and it led to many unpleasant limitations on what was available to buy, including some pretty savage shut-outs of perfectly good games.
the floodgates are seemingly open, but i'm a big boy now and i'm pretty okay with being the master of my own mispurchase destiny. i can see the issue of having shitgame: repocalypse's name broadcasted without prejudice to millions of cud chewing punters, but i think the key here is transparency and availability of criticism.
it's not talked about much, but i'm finding the steam review system pretty fantastic. you often get a wide spread of surprisingly eloquent and on-point critique right there on the store page - it only takes one scroll of the mouse wheel for any prospective buyer to discover that rekoil is a game nobody should buy in its present state.
such is steam's monopoly, for valve to start a process of stamping every title with their official seal of approval would be akin to censorship of the platform. i don't think it should be for steam to make the road any less dark and full of terrors, just continue implementing tools to help us navigate it.