Has anyone done the research on the health benefits of rubbing broken glass in your eyes twice a day? Somehow I doubt it. Would you say that we know nothing about it? Personally, I am quite happy to accept based purely on common sense and intuition that this is unlikely to be healthy.

Research is just another tool. It happens to be a really good one, and when research contradicts common sense and intuition, research usually wins. ("Usually" because it can be flawed, just like anything else.)

But in the absence of research, we can still do better than just saying "uh, I dunno" in many cases.

The alternative isn't reasoning based on buzzwords, it's based on thought and available evidence. No, that's far from perfect, but it's also not going to lead you into homeopathy, reiki, psychic surgery, or acupuncture. Flossing has a plausible mechanism of action, unlike any of your examples. If it turns out that this plausible mechanism of action doesn't actually have any long-term benefits, then that sucks, but it doesn't mean we should give up on thinking about anything that hasn't been researched.