I mean spy is a little bit overrated you are right.
When you watch vids from swipez or Mr Paladin, you might think spy is Overpowered and it is what makes him overrated : The belief that spy is an invicible class.
However, only a god spy can make spy op.
If I go agaisnt really good players and just new players that dont know how to strafe, you wont be able to do trickstabs and you wont do much stabs. In comp 12v12 (Highlander I think), the role of the spy is to kill the medic and let your team to have an uber avantage. It will be really hard for you to do crazy stuff otherwise you will get kill immediatly.
So I cant change your mind becausr you are right, spy is overrated if you compare him to other classes that can do much more kills than a spy that would always get kill due to good spy checkers.
The only place where spy isnt overrated is casual. In casual, players easily fall for trcikstabs and a really good spy can win the game single handedly by trickstabbing everyone with a kunai (and trust me it is really fun).
To conclude, spy is a little bit overrated even with his capacity of one shooting everyone because onmy good players can make spy work really well in a game.
This is my opinion of spy rn in the tf2 "meta". I would be pleased if you can correct me or change my point of view.