they really should've made a movie about Doug 10-15 years ago, back when the show was still airing
That would have made sense BUT its kind of a fun nostalgia type of thing. A lot of people who grew up watching Doug in the 90's are now in their 20's. Its a good throw back and the way they did this is almost as if Doug came back to Bluffington after his 90's days.
Kind of a cool coming home type of thing. I also believe they made a Doug made for TV movie.