Clint isn’t a stupid guy. In the show, he’s hard of hearing, which some people might mistake for being dumb if they saw him on the street, for example. But remember how scary he was in The Avengers. Guy could shoot an arrow into the wind and knew it would blow up an engine. You know there’s some crazy subconscious math going on there. Also, his counter-terrorism rampage in Endgame wouldn’t have been nearly as successful if he wasn’t a great planner and tactician.