I see your point that they could have more categories, but they do have some and they have been previously used.

Curable/incurable = white line or no white line

Enhancements
Conditional Enhancements
Enfeeblements
Others

To show how this has been used in the game:

The Warden's Paean - Removes one select detrimental effect from self or target party member. If the target is not enfeebled, a barrier is created nullifying the target's next detrimental effect suffered.
Erase - Removes a single damage over time effect from target party member other than self.

Erase is similar to the "remove poison" idea, but was removed from the game due to lack of use (since casual players weren't gonna bother), while the Warden's Paean remains although is probably not used a lot either. It's the sort of thing a good player uses as skill expression but most average players just wouldn't be likely to touch.

So I think based on what they did with Erase, they could distinguish enough to make abilities remove specific types of debuffs. But whether SE will bother with something that the majority of this game's players don't end up using, I don't know.

I'd like it if they did bother. I used Erase all the time. I used all the role actions, and I noticed the rare players that also used things like this. But it was clearly the minority of players that were trying their best, and not the majority that barely knew what they were doing/returning to the game etc.