So, what you're saying is that the problem of philosophy is that someone could derail a discussion concerning ethics by simply asserting meta-ethical subjectivism and that would be uninteresting or bad in some other way...
I don't quite understand this objection. Not to mention that this is exactly the opposite of what you would expect to find in a philosophical debate. The whole point of the discipline is that every position must be argued for and questioned and not just asserted. That of course includes subjectivism.