I think that is sensible for most people. However, for me, there are three reasons why watching bad films is never a waste of time:

1) Most obviously, because I am essentially self-employed to watch and review new cinema releases (it's part of my writing income, per my Simon Dillon Cinema publication on Medium and Substack subscription service).

2) I'd actually argue a cineaste is defined more by how many bad films they've seen than by how many good.

3) Perhaps most importantly, as someone who also writes and releases a lot of fiction (novels, short stories, and occasionally I get commissioned to write screenplays), the study of failed storytelling - in books, plays, films, etc - is just as illuminating, if not more so, than the study of storytelling that works well. A bad film can be hugely instructive.