We will have to respectfully disagree that Bruce Lee couldn't fight or that he was overrated as he is the godfather of mixed martial arts. The point was to illustrate that knowing a bunch of techniques was not the way to approach a fight but rather simplicity was king.
He's hardly the Godfather of MMA - not historically, nor in terms of what he did, although a lot of people seem to love him for his movies (and never seem to want to adress the PED allegations made by one of his biographers). If anything I'd say he was a pin-up on the MMA fighter plane. But we can respectfully disagree on that, too
And your last part as I pointed out earlier is how professional athletes are selected.
For instance people talked about how static stretching before a baseball game or lifting was a great way to warm up. It was popular consensus that it was actually the thing to do before a contest and later on we realized that static stretching doesn't do much of anything for most sports and could very well lead to injury and will lead to a lack of performance.
History and training philosophies tend to be dialectic - usually, first someone says "A!", then the next guy goes "B!!", and finally, someone comes along and says "A and B both have their merits, provided that the following conditions are met: ...". That may then become the new "A" and so on.
Of course no training system will make 99% of the population a professional as politics, injuries, money, generally being in the right place at the right time all matter as well but the point is to train optimally to give yourself the best chance at success at whatever level you are at.
Actually, I think that's one of the few blanket statements I am willing to make: 99% of the population will never be top fighters, regardless of what they do. The top fighters by definition will always be the most gifted, most willing and the ones who (whether by chance of intelligence) figure out a way to stand out from the rest that works for them.
I have said it before: the goal of a school is to continously produce as many top guys as possible, and the goal of the individual is to be one of those. It is never in the interest of the school to use "idiotic" methods, because that goes against the goal; if they stick to a method, usually it is because it seems to work for most people. If it doesn't, it will be adjusted soon enough - although that may of course be too late for a givien individual to still reach their full potential.
However, it is imho unwise to disregard the knowledge of schools entirely, especially if they do succeed in producing top athletes. Also, I would like to repeat my earlier point that everything needs to be seen in context, that is how that school generelly trains. If your school emphasized sparring and my school emphasizes drilling, we will each need different strategies in our extra training to allow the method to work. If I used the methods ideal for your approach and you the ones for mine, we will both likely end up with sub-par results, unless by sheer chance we happen to stumble unto something that was previously holding us back.