I understand your point well.

Let me restate in another way. Any MA techinque should improve any untrained fighter. Of course that doesn't mean the next guy you go up against will not be a better fighter.

So no, MA does not guarantee a person the ability to beat an untrained fighter. It does however help a LOT, for a person to be able to fight, that had no fighting technique previously.

One exception on that front. Take a person who can already fight pretty well, at least decently without any MA training. If this person takes a MA for a while, and begins overthinking things, his abilitiy in a real fight may actually decrease. If he does A, I do B, if he does B, I do C, etc, etc. This can be a real problem for a person who already had a clear mind before MA. When I say clear mind, I mean before formal training, when in a fight, you pick your targets, and get to them anyway you can---> no preciceived techniques, just intention and action.

I am not saying all MA schools teach this way, but unfortunately, some do.