Maybe Tag exclusion would help for experienced users. I still think separate sections for games based on what they really are would help. Strict moderation would also help.
So you want Itch.io to become just another Steam. How is that going to keep the lights on at Itch.io, once they lose one of their key unique selling points? They are a haven for experimentation. "Fail fast, fail forward, and learn from it", is the motto I see many devs on this site following. If we open up an Itch Greenlight program, then we're nothing more than just another Steam.
Coming from experience as a business owner myself, I can tell you that me-too businesses never work out in the long run. Either they reinvent themselves to compete more effectively with the business model who they copied to get into business, or they go belly up. If you're trying to make Itch.io a facsimile of Steam, and if they follow your suggestions, I foresee that we're all extremely screwed. Also, where will people go to find niche sites where they can share their game design experimentations with, then?! Nowhere.
There's a reason I don't use Steam. It isn't because I'm afraid of quality. Coming from a family with one half a lineage of engineers, scientists and medical practitioners (the other half being military leaders, but that is kind of irrelevant to this discussion), I value experimentation and the ability to do so, quite heavily. I was raised in a household that valued exploration and curiosity, and so I value that myself, and which is why I like hanging out on Itch.io rather than Steam. I may never use Steam in the next decade or so... but I'm already here.