Nice straw man argument. You're right, there is no point between giving up 0 ppg and consistently having teams shoot above their normal %.
Are some shots truly low % and contested yet go in? Of course. The problem is that after every game this happens, they see somewhat contested shots going in and think this is pure chance. Some shots, some entire games, maybe. If you want to watch great 3 pt defense, watch Monte in Forte 2 years ago on Stillwater. It was a huge difference between what we typically see. And most top 5 teams can take a shooter like that and get him out of his rhythm.
Were 33rd in defensive efficiency, after spending the last few seasons in the 70's. Sometimes guys make shots and sometimes we miss shots and sometimes that (amazingly) is what decides basketball games.