Their successors forgot that however thin, the underlying movie has to be watchable, or you lose something. Maybe it’s just generational (always have to allow for that at my age), but I kind of think that Scary Movie et al is stuff that is not nearly as timeless.
That reminds me of one of the major keys to the success of the ZAZ movies, which was to hire a cast known for their serious, dramatic roles, a type which Nielsen epitomized. At no point could the actors indicate that the situations going on around them were funny, otherwise the illusion might be punctured.
Perhaps some of the later imitation films, like Scary Movie et al, kind of drifted away from that premise, I don’t know.
Speaking of Blazing Saddles, I recall reading that the musicians and orchestra were told that they were producing music for a classic-style western, and when they ultimately learned that the movie was an intentional farce, they were not amused.