It improves. I'm not the best salesman for it. Most honest fans will tell you the show is flawed. It's monster of the week for most of season 1 and starts getting interesting around season 3.

Season 4-5 are considered the best. Season 7 it starts dunking on itself and it's premise, and becomes more cheesy but with a lot of found-family/parental trauma motifs (everyone in supernatural has beef with their family.)