I'm probably one of those who'd prefer more discussion related to folk and blues music, although I've never before stated it in a thread. Mudcat will be what it will be, and I doubt that the most curmudgeonly of the 'folk and blues music discussion only' crowd will have any great effect on its evolution.
For me, the result of the mix as it exists presently is that it takes me only a fraction of the time I used to spend perusing Mudcat threads. OTOH, often my wife asks 'did you hear/know....?' and I'm suddenly reminded of some thread title, over which I skipped, that probably refers to the subject of her question. And, about 90% of the time, it does.