Ernie and Bert being in the movie: Good. Their roles in the movie: Not so good. They live on the street with everyone else. Why were they not directly involved in the adventure.
I shouldn't have to reinstate the main reason the film was to sell Elmo toys, and the reason we even got a second theatrical Sesame Street film was due to Elmo's popularity. FTB "got it right" because even though the movie was about Big Bird, it wasn't Big Bird the movie. FTB was supposed to be an ensemble piece, EIG wasn't. FTB is a Sesame Street movie, EIG is an Elmo movie with other Sesame Street characters in it. Even the ones that went on the adventure with them were barely there. It's obvious to me this movie was rushed out to cash in off the plush toy. FTB was made for the sake of making a Sesame Street movie to go along with the three other Muppet movies. Had FTB did better at the box office, I think we'd get a true follow up instead of something that was kind of cynically produced.
Plus, this was before Oz's roles were recast, so Frank was busy with other things. If Ernie and Bert were in the movie as a whole, Bert would have been performed by someone else and dubbed in later. And while not necessarily a bad thing, I feel that's a huge problem with MFS, putting too many of Frank's characters into one scene just for him to dub over all of them. Fozzie, Piggy, and Animal felt a little distant.
Though there's one thing I must reflect upon. EIG used Ernie and Bert in a way Statler and Waldorf
should be used in a Muppet film. I don't see why they never bothered making a Muppet film where Statler and Waldorf actually stop the film to comment on it.