I don't think that's quite fair. Some shows are more obscure than others. I'd use Parks & Recreation as an example of a "marketed as non-mainstream" show. It's not as popular as The Office, sure, but pretty much everyone has heard of it.

Louie is a bit different. Most people haven't heard of FX, and of those that have, most people haven't watched Louie. So while not obscure like "one copy of this book was ever published", it's not "mainstream" like Seinfeld.