wtf happened to steam filters?

"Filters" are likely based on user-defined tags, and not the genres that devs define for their games, but those dev defined genres merely link to tags. Since devs only define their game as being in a few genres, but users will tag a game with many more tags, its all in the eye of the community beholder.

Quite frankly the Steam Labs stuff is probably better for finding certain types of games than browsing games with tags.

Adventure is a very broad term to use for games now.

"I had a great adventure killing monsters and escaping mars"

then how to filter classic adventure games?

Few days ago found out Fall Guys and Mirror's Edge are racing games, haven't considered this but now I can approve it's correct.
Just like puzzles, there are lots of different ways to create a puzzle. Even CSGO can be a puzzle, you need a specific route and tactic for the solution of winning a round :lol: and every round is an adventure :lol: