Why can't I reach the students with real gaps or real fear?

You have gotten good. Most students now move forward under your hand without much trouble. Then one arrives with a real gap, or real fear, and something in you reverts to guessing. You cover it well enough to get through the hour. But you know the difference between teaching and performing competence. This is not proof you have reached your limit. It is proof you have outgrown your old method and built no new one. Winging it worked when the problems were simple. It cannot work on a gap that goes back years, or a fear that has nothing to do with the material. Those require a deliberate approach — and you do not have one yet. That is the whole problem, and it is a solvable one. You do not need more talent. You need to sit down, before the next hard case, and build the tool you have been missing.