Besides the capability to exclude tag(s), I think Itch.io should make a new classification for game's demos/trials. A bunch of those are tagged as "free" even though in reality only the demos are free. And this, obviously, could mislead gamers.
That being said, I'm impressed with Itch.io's extensive tag system (even though some of those should be merged, like the "tentacle" and "tentacles" tags that I brought up in my thread here https://itch.io/t/579083/how-is-the-tag-system-here-handled#post-1004287); the ability to make my playlist/library "private" and the wealth of information that I can find on each game's pages.