When an army gets a new codex, this is the best time to get into it. You have a whole breadth of other players learning along with you on how to play the army. You also have that fun element of surprise for the uneducated folks who don't know what the Tau can do
Dunno about your meta, but in mine, Tau, Eldar,
BT, and
SoB are the least played. Those codecis sometimes throw me for a loop, but I have seen other players completely caught off guard!
As for the greater good, you need to realize that Tau are not Space Marines. Their army needs to be operated under the notion of synergy and not brute force.
The great thing about Tau is that they bro-fist with just about everyone. So unless you play 'nids, you can start a small allies force and expand into a playable army.
Tau are the first 6E codex I bought and I'm loving the reading. I will definitely be investing later this year or next year into a Tau army.