DH

Well all of that is summed up in the old boxing refrain; "Everyone has a plan- until they've been hit."
Since my teenage years- when I would pick on martial artists to show they were full of crap- I have said much the same thing. "If you haven't fought you don't know how to fight." And even then there are skills to learn in fighting. On the whole being booted in the head, stabbed, beaten with furniture, and coming out on top of a room full of bikers will change a persons mindstate, readiness and ability to deliver. Most assuredly the way you respond to threat and where your mental state is when someone decides to screw with you. Being able to "deliver" is best judged after having been pummelled-on and you keep coming.
Also expressed in the phrase "It isn't the size of the dog in the fight-it's the size of the fight in the dog.
Anyway sorry to be contrary but I see it as a far more simple puzzle, best expressed in Chuck Yeagers terms on how best to make an ace pilot. "Experience, experience, experience."
And he didn't mean in a flight " simulator"
For some people this is BTDT. Men who have been in the real shit with their lives in their own hands. For others getting closer to all out doesn't have to be life endangering- you can up the pressure in a safe but full-on and edgier setting, were most waza falls apart, but life-endangering does have lessons all its own.
Another good bet is to at least train with someone who has. Folks may see a different outlook from them VS a more typical teacher or fellow students as to what actually works; and the where and when.
Another Old dog Budo guy once said "The best thing that could ever happen to the present Doshu is to have him dropped penniless in some backwater rough-and-tumble place that hates foreigners. If he makes it back-he'll be a different man."

As for waza? There most certanly techniques that are stupid in any real applicable way. And those will always be hotly debated from the suburban dojo guy who has never been in a fight in his life, to those who love taking people efforts apart. They? Will never agree on what "useless" really means.