As has been pointed out earlier, this collection is missing the first six entries in the franchise, namely The Muppet Movie (1979) The Great Muppet Caper (1981) Muppets Take Manhattan (1984) The Muppet Christmas Carol (1992) Muppet Treasure Island (1996) and Muppets From Space (1999)

From your contribution bible:

As a general rule, a sequel is a film which centers around the same main characters and continues the story of an earlier film. The protagonists evolve and are aware of the events that happened in the earlier films.

These films center around the same main characters and continue the general story of the Muppets' adventures. The protagonists evolve as much as a group of slapstick puppets can, and they are certainly aware of what happened in earlier films. Not only are these films valid by your own rules, but they are also directly called out as sequels in Muppets Most Wanted (Dr Honeydew refers to Muppets Most Wanted in-film as "The seventh sequel to our original motion picture"). Just because they were part of a remake/franchise revitalization does not exclude that the ones currently standing alone in this collection are the sixth and seventh sequels to The Muppet Movie.