If you need an explanation of what art game means, then how are you going to decide if the tag applies to your games or not? For what it's worth, each tag on Itch has a description (and if it doesn't, you can suggest one). And pray tell, how does game discovery work on Steam? Because from what I heard, you can find games there that don't even work. Like, at all. I'll take an artsy-fartsy game that actually runs any time.
Even in the search results, games on Itch.io have taglines and genres. I can hover the mouse over it to see screenshots. If a game sounds interesting but I'm not sure about it, I can easily click through and read more details. Including a complete list of the tags the creator thinks apply. If I'm still not sure, there's always the option to try out a demo. Often even the full game. What more can I possibly want?!
Please, PLEASE stop assuming. Stop pigeonholing people and ascribing imaginary behaviors to them. They're smarter than you give them credit for. They can search for both "art game" and "trash game" just fine. And yes, they can use both Steam and Itch.io without confusion.