Even well before Monteith's death, the show developed a lot of problems after a rather terrific first season. Season two was wildly uneven. Most of season three was just unwatchable. Season four was half good (New York) and half terrible (the new students at McKinley). Season five was still inconsistent, but had a couple of really good episodes (in particular, the two emotionally-charged Monteith-centered episodes). The show just fell victim to bad writing, and even if the final episodes are really great, it won't be enough to make up for the slog it has been to reach it.