There are many good reasons to think that dark matter is a good solution to certain cosmological problems. There are also a few good reasons to think that dark matter is total BS. It is a genuine open question. No theory in this area is a good fit for all available evidence.

This is not a case of "progress by funeral" like, say, the Alzheimer's situation also on today's front page. The linked article is a good summary.

Anecdotally it seems like, inside the scientific community, the dark matter skeptics are all in the older generation.