Which tank should be played and when?

I recently started maining tank after returning to this game after a while, but I actually wanted to learn how to play this time, instead of running around in quickplay.

I think my biggest weaknes is not understanding which tank to pick depending on the game. I struggle with identifying comps and don't feel so sure if I'm doing it right because some of these games feel so close, and I can't help but feel like I'm the reason behind our loss.

I'd appreciate if you guys recomended some tanks for each comp style. I currently like to play Groot and Thing, but all of the vanguards in this game looks fun so I don't mind adding them to my champ pool.