Why are there 2-3 exhausts in almost every game?

It is meant to be a spell for supports to help them disable/kill/run away from enemy champions, not a spell for skirmishers and assassins to make them auto-win any duel and be much safer, or battle mages doing the same thing. just outshines almost every battle spell right now for most mid/top laners and almost every single support except maybe Thresh or Bard. The 10 MR/Armor reduction on the spell is just unnecessary power, and removing it would make room for other spells such as Ignite or Barrier. Exhaust has became a cookie-cutter spell in this damage-heavy meta because its really good in both offense and defense, and lowering it's offensive capabilities would help a lot. The spell would certainly still be picked very often, probably in every game, but there would also be more spells, and wouldn't be 2+ exhausts every game.