The filters aren't on by default because the "fail" state (not noticing the tabs) is the game is playable but you have to scroll a bunch when you level up. If they were on by default the "fail" state would be that the player doesn't have access most of the talents.

I agree they aren't the most obvious but at the same time filter tabs are something that be expected of the kind of player who would pick up an involved game like this.

You are right though that the leveling UI is pretty crap and needs to be its own full-screen overlay.