Why not Taric?

a gem god.

Taric benefits from all of the popular support items at the moment due to his unique skillset.

synergizes perfectly with his ultimate as well as the fact that he has shields and heals, both of which scale off of his hp, and the cdr is nice for any support.

also synergizes with the ultimate, letting your allies survive until the invulnerability kicks in, also adds armor and magic resist to taric which makes him tankier while increasing his damage through his armor scalings.

aoe heals, point and click shields.

huge armor, lets taric position better around his carry so he can stun more easily as well as makes it easier to stomach linking with a diver.

Taric also turns any diver you have in your team into a hard engager. Meaning anyone who can get into melee range easily can fulfil the role of tank for your team thanks to Taric's kit.

Taric has ok damage thanks to his passive.

Taric doesn't really have a weakpoint in his kit since he does everything supports need to do, cc engagement, cc backline, protect the team.

TL;DR:

Why don't I see more Taric? He can protect the front and backlines at the same time while providing a stun threat and he synergizes perfectly with the top support items thanks to his unique scalings and tanky body.