Take ignite instead of exhaust when you’re playing Thresh, Blitz, or Brand.
A lot of my teammates have told me that exhaust is better when against Zed, but I’ve found that’s mainly winning your lane is more important than trying to carry late game when you’re playing Thresh.
Start building CDR instead of just tankiness. It looks like the maximum CDR you’ve reached is 20%, even after you’re level 11. In the words of BunnyFuFuu, Thresh is more of a CC caster than just a straight up tank.
If you want to make more plays (since you claim your hookrate is really good), getting CDR by rushing kindlegem against AP to build into Spirit Visage late game or Glacial Shroud against AD to build into Righteous Glory late game will help your laning phase A LOT.
You probably already know this, but Thresh powerspikes at level two. You can use this, but more often the chances come when your enemies get too confident. The hooks I hit the most are hitbox curves around/between minions and ones in chases because I know where they would dodge - the more you play him the easier enemies are to read.
Know what your abilities are capable of. For example, saving flay if the enemy has a Zac to stop him from 4-man knocking your trash teammates. Using it to stop Khazix jump or deny Tristana jump.
Also,
TL;DR:
-Take ignite
-rush CDR
-hit hooks
-and obviously, make the right calls. This can be difficult because 1. Your teammates may not cooperate, and 2. It can be hard to tell the right call at times. Sometimes it’s crystal clear, like when the whole enemy team is aced and none of your minions are close to their tower, to go for baron or drake.