PSA: Taliyah is not a Support.

Her damage falls off massively as the game progresses compared to other mage supports, her utility alone can not come close to making up for it (her slow is not good, is tied to a more important function, her shove is on too long of a CD to be a viable solo utility ability, and some of her utility like the E dash penalty is AP reliant), and her laning is generally mediocre, with a large risk of turning into feeding if she falls even a bit behind against an aggressive lane.

I can pick a better Taliyah for support. I can pick stronger laners that get better damage scaling with better utility. They'll even be almost as good at roaming because they're just stronger earlier and they aren't ult reliant to gank. The only thing she does from a support perspective that I can't do better with someone else is the wall, and that just doesn't make up for everything she's bad at.