Who cares that a coach is 5 feet onto the court while the players are playing?
Poor take on your part.
Refs have never, ever, been militant about enforcing the coaching box, or penalizing coaches for being on the floor during game play.
Officials have a lot to worry about besides making sure the coach is in the box. But a warning and then a T would solve the problem pretty quickly.
Outside of the box but still on the sidelines is one thing. I don’t care about that so much.
On the court while the game is going on is a whole different thing.