Obscure shows

I've tried searching up some obscure shows on Serializd and they didn't pop up, this is the only major problem I have with Serializd, is that obscure shows aren't really on there or are but don't have any seasons listed and the poster isn't there. However, on Letterboxd this isn't a problem. Why is that? They both use the TMDb database, no? FYI, adding anything to TMDb is a hassle and I'm not willing to do it again.