The thing about RM, is that what works for them wouldn't necessarily work for other huge clubs. A guy like del Bosque would have been a miserable failure at United or Bayern, but he had just the right touch for the Bernabeu. What I find curious is that St. Mirren thinks that Guti might might be a good fit for them.
I always was very critical of Del Bosque, kind of using similar reasonings to the one you made, but almost every player I know has him in great estimation, so he probably did something well. I remember someone, an academy player (I don't remember the name) saying how his training sessions were much better than the ones of his sucessors. Ronaldo said he was one of the best coaches he had, that he was an excellent man manager, had a vast football knowledge and could transmit the essential stuff in 5 minutes while others would need one hour and a half. Roberto Carlos also had a similar opinion, and said he was one of the best he had. Roberto Carlos had Heynckes, Capello, Luxemburgo, Queiroz, Hiddink, plus the ones at Brazil etc, so that says something.
It's also impossible to know what he would have done at United or Bayern. It's useless to imagine the outcome. In 2000 Madrid were horrible before his appointment, he switched to 3CBs and 2 wing backs with Redondo alone in the middle and the results started to be good again.
Just because some successful coach doesn't shout all the time or lacks an aggresive aura on him, doesn't meant he isn't damn good at what he does.