User blog comment:MaverickGuy720/Was the movie too early?/@comment-32173189-20180428042326

Nick might have realized they were jumping the gun by giving the series a movie so early among other factors. Considering the current situation the show's staff not only have the main series to work on but an upcoming spin-off as well, and the transition to a new show-runner in light of Chris' firing. Not only that but the movie will likely have a higher budget than the show and coming up with plot to set it apart from show (so it does end up being an extended episode) will likely take some time.

But it also seems like this situation is similar to the Simpsons in a way, in that the season 4 episode "Kamp Krusty" was originally pitched as a plot for the movie, but was instead made into a regular episode and the actual movie itself didn't get released until 2007 and the reason there hasn't been another movie yet was (by the current staff's own admission) that first movie was very taxing ordeal on them.