It's pretty questionable. I don't really mind laxer policies when it comes to certain content (adult, gorey, whatever) as long as there's a big warning when you select one, but no curation at all... I mean, that's pretty much what they were doing anyway. Ever since Greenlight at first and now the "pay 100$ to get anything on Steam", it's been so easy to just flood the place with garbage. It's kind of a difficult issue anyway, because while you want to keep out the 10 minute Unity tutorials with changed assets, there's never a clear line between "garbage" and "worthwhile game". There's still a fair amount of people who will call anything with retro graphics "outdated garbage" or similar, especially if you look at some of the hardcore console fans. At first it was kind of too difficult for very small developers who made decent games to get on Steam, but this isn't really right either.
Here's the thing. You mentioned this:
It's kind of a difficult issue anyway, because while you want to keep out the 10 minute Unity tutorials with changed assets, there's never a clear line between "garbage" and "worthwhile game".
This is exactly what curation is. Valve is being a panzy ass and doesn't want any bad press, so they said "Screw it! Everyone's in!
Except for illegal products." They unfortunately caused this issue themselves. Valve had been increasingly subject to pressure from random places on the internet. I remember a controversy quite couple of years ago where they decided to remove a game and people cried "censorship". If Valve had simply said "We're a damn store and we don't want to sell this game, get over it," none of this would be happening. Instead they eventually released Steam Greenlight. Ever since then, Valve has been digging themselves further and further into a hole, standing their ground about not curating the garbage that goes on their store.
I'll say it again and again, Valve used to curate. That was over 5 years ago, before they started greenlight. Any misconceived notions about "What should be allowed on steam" foremost stop at what is illegal, then what Valve decides. Unfortunately, Valve decided to stop deciding. There is literally nothing stopping them from hiring a staff of 100 people to playtest and sanity check games. If people want something new, like how Valve claimed to be oh so surprised about visual novels, they can simply adjust the composition of the curation team to allow for such things to happen with a petition on their forums. Did enough people show interest? Great that means this thing will sell.
A triage system would do wonders for curation: Every time a game gets submitted to steam, a bot checks to see if it has an executable, malware, or even functions; the basics, Valve loves bots, and supposedly they are doing this already. If the game passes this test, send it to 10 people on their curation team. These people will assess the base quality of the game at a glance. Does it look like an asset flip, does it contain anything that would be offensive or against company standards, is it illegal. Next the game gets sent out to the next 3-5 people. These individuals will tag the game with the most obvious genres it contains by the screenshots and promotional videos: FPS, RTS, Multiplayer, Action, Puzzle, etc. That's it, done, nothing more. Finally, the last 80 people (or however many they need) will be sent the games that they are "proficient" in, and a random sample of games in other genre. These will be the people who actually play the game. They will then give a pass or fail to the game, and note down why. If enough people, say 70%, give the OK, the game gets admitted. If it fails, they send the game back to the developers and tell them why. Virus? Asset Flip? Misleading and or inappropriate promotional material? Game didn't meet quality standards and the playtesters didn't feel it was worth being sold? If they then said they had a three strike policy, where you had 3 tries per year without a successful game being admitted, you couldn't submit for the rest of the year.
Unfortunately, it's in Valve's interest to not curate. They have integrated all sorts of metamarketing into their systems from achievements, trading cards, and marketplaces to allow for the lowest quality shovelware to make them a sizeable amount of money for the few people (whales) actually want that stuff. This is ultimately detrimental to the entire ecosystem as it's making actual quality games harder to find. The AAA games corporations are advancing around this with advertising, but the smaller indie game publishers are getting washed away in the sea of shit. With all of the AAA games companies slowly creating their own stores: Origin, Uplay, Windows; and probably more to come (I wouldn't be surprised to see Bethesda make a store), Steam is going to lose the AAA market. With the AAA market gone, all steam will have left is it's ocean of shovelware and indies; the shovelware outnumbering the indies 100 to 1.
Any sane person can see where this is headed. With the AAA market moving on to fewer and fewer games, all sustained by microtransactions, they
will move away from steam so they don't have to pay Valve the "privilege" for them to take 30% of the money they make. These companies are making enough money that they can host their own services, and market their own games. Gone are the days when being on Steam was marketing enough to sell a game because everything on it was a major published game, or from a company who had a good track record. Valve is being shortsighted with this decision. Steam will stay around for a decade, but by the end of it, unless they start literally cleaning up the shit they are selling, they won't be a market leader.
TL;DR: Valve needs to stop being such a fucking pushover and start curating. If people cry censorship, Valve needs to laugh at them and tell them it's their business, and they will run it the way they see fit. If they don't, they won't be in business after a decade.