It IS too late for steam to turn back. Are you aware of what Valve ultimately are transitioning Steam into?
The basic gist is for Steam to become completely open to self publishing, but to have multiple users and groups creating their own curated stores within steam. So as well as Valve, there could be a Yahtzee store, TotalBisucuit Store, GiantBomb Store, Ubi Store, Cyberpunk Store, Bag of Shit store etc. Users, Devs, Pubs or whoever make stores would get a cut of the sales they create just as other people creating content do in TF2, Dota2 and a like. Gabe has explained the idea in previous years such as here:
http://youtu.be/t8QEOBgLBQU?t=43m42s
As for worries of the quality dipping with the inevitable dumping of shit on to Steam, as we are already seeing, that has not been made clear too clear. However, a few weeks back some indie devs went to Valve to see where Steam is going. One of them is at least perfectly happy with how it's going to be particularly with those issues in mind and visibility of their own content:
http://positech.co.uk/cliffsblog/2014/05/10/the-future-of-steam-vr-and-other-seattle-stuff/
Still, we'll have to wait and see how it goes. One dev at Steam Dev Days claimed Valve have told him that greenlight would be gone by the end of the year, which would make the new store implementation likely before then. Right now though, Steam is a mess. The only explanation I can think of for how messy it is could be that they purposely "open the flood gates" to a lot of shit content specifically to test internally how their new system handles it... otherwise I have no idea