Every coach I know HAS done his chosen sport, just like every MA teacher I know HAS done his chosen MA.
They may not h ave competed at a high level or even at all, but ALL of then HAVE experience in their chosen sport.
Marc Laimon is a good MMA grappling trainer who never fought.
Cus D'Amato and Angelo Dundee are boxing trainers who never fought. Dundee is in the International Boxing Hall of Fame as a trainer.
I don't know Marc but I am sure he has more than enough experience IN HIS Sport to teach it.
As for Cus and Angelo, they did fight, you don't box without fighting in their day.
They may not have had impressive records, but that doesn't take away from their amazing teaching ability.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !