I think that a rider who really wants to make progress and lives in an area with some options will eventually find the trainer that works good enough for them.
I would also say that low aspirations are not the same as no aspirations.
An older ammie with confidence issues, maybe some health limitations, and a safe but greenish off breed horse wants to eventually school and show first level but maybe also wants global skills to feel safe on easy trail rides. That person might take a long time to be comfortable cantering or pushing up into a true working trot, even. But they also need the reassurance of regular lessons. They have aspirations but they are low, and might be very slow getting there. They need a competent instructor for their level.
On the other hand there are adult ammies who say they want to “go up the levels” but don’t do their homework. Sometimes that’s because the advice they are given in lessons feels scary or unpleasant to do alone, especially if they are in a crank and spur program where the horse gets angry when ridden “correctly.” These I think are probably more frustrating to a coach because the clients will talk big but not follow through with their homework. But again these aren’t exactly even low or no aspiration clients. They just aren’t honest with themselves.
IME these clients are an ideal match for the trainer who also talks big but can’t really get results. Both sides will talk big and blow smoke but neither side really expects progress after a certain point. At a certain point the rider moves to a new trainer or starts over from zero with a “better” horse or stops riding altogether.