I exaggerated a lot when saying that it has no predictive power, you're right. However, it is very much true that different galaxies have different amounts and

I exaggerated a lot when saying that it has no predictive power, you're right. However, it is very much true that different galaxies have different amounts and distributions of dark matter. There are many broad categories, and certain models about galaxy formation try to predict these, but not all galaxies fit these models. This has two effects: for one, for any galaxy with unexpected dynamics, you can fit a dark matter distribution to explain the dynamics (but! This is not unbounded, it still has to match certain other observations). The other effect is actually in favor of a dark matter approach: it means modifying parameters of our theories in a general way has little chance to reproduce the same properties, as each different galaxy is different.