There is no fucking reason to ask for another Season right now because the show developed into shit.
If it ended in the movie the request for a new show would be double or perhaps even triple the actual number.
Additionally, tons more of these different theories that fans were working on would flow the internet a lot more.
Remember when Toffee and Marco were said to be linked because of the dark chapter written by Eclipsa?
Before the cheeks were shown in S3 there were a small number of "crazy" fans out there theorizing that Marco was a Butterfly, said theory developed the moment he took the wand in S3.
Star was sniffing Marco's hoodie... something that curiously was done long before S3.
And so on, there were tons of theories, people were expecting a lot from the show, and not for nothing, they wanted something interesting because from S1 to S2 they developed characters, placed an interesting villain that was doing some nice plotting, created this problem for Star between having responsabilities because of her royal line and wand charge and her feelings as a teenager, and a large etc.
All of this was slowly destroyed, things that were more or less worked on and were expected to gain sense in S3 didn't happen, there were things that seemed to be pointing at some place, they seemed to have lore, and should have gone somewhere but were completly forgotten.
The autistic child shouldn't have been given a show, or on the worst case scenario, she should had been stopped right after the movie.