I highly doubt without some moderation this will work.
People tend to do things unless explictely deterred or not allowed in the first place.
e.g. There is no u-turn sign (though in the area it is illegal) people will make u-turns regardless, unless cops are watching over them.
Same thing here. People will still post AI slops unless there are some watchers.
Steam can increase the barrier to entry to prevent flooding the market, of course. But AI will facilitate making more games of increasing quality. Today it's all slop, but that may not be the case tomorrow. So what we actually need is a trusted curation system so we can float the garbage out and find the gems.
And as much as I appreciate Gabe, there are enormous financial incentives that make me uncomfortable giving yet more power and dominance to Valve. Especially as he gets older.
So this is a space where games journalism has a space to get back in and try to innovate solutions to a real and growing market problem.