The low-budget aesthetic of this opening comes from (besides the necessity since they had very little money!) Joel's original vision of getting down to the level of the movie of the week and embracing the corniness. It wasn't about looking down imperiously at the movie and mocking it for its failures as much as it was about celebrating the movie by throwing a whole corny party surrounding it, including sketches where they reproduced the low-budget antics of the movies they watched (in later seasons the perspective became more downward-looking while still remaining a great series).

They forestalled serious fans of the show from getting overly attached to the characters and fictional premise by being so flippant about how 'it was just a show', staving off a potential "Trekkie syndrome" as the show became popular, and keeping the fanbase "real" and down-to-earth (pardon the pun) about their favorite show. At the same time, there's just enough professionalism allowed to shine through that a first-time viewer can sense the intention behind the cheesiness and not turn away in embarrassment.

Anyway, this is a wonderful example of working within your means (on a truly indie production where all actors were also staff) and making the end result charming and appropriate to the subject matter.