Well I am not responsible if people dont have imagination alright. There are a million scenarios that can be reached from this point on. Finishing it here would either mean a sudden axe or author burn out. This sand castle isnt close to being finished.
No one said you were? And that's not how writing works.
A story doesn't end because it's exhausted every possible permutation of the scenario, it ends because the core narrative established from the beginning has reached its conclusion and the majority of side-threads have been either wrapped up or reached a point where their continuation doesn't need to be shown.
Baiser has already dom'ed both the magical girls and her own sub(ordinate)s into growing as people, accepting their flaws and weaknesses as parts of themselves and reaching higher levels of power and gayness friendship, the only plot-threads left was to reach a climax in the conflict and show what was up with the mascots this whole time.
Both are threads which were coming to the forefront in this last fight, with Baiser going berserk due to the mascot's ulterior motives. Literally, if the magical girls and bad girls had come together to ultimately defeat Baiser, only made possible thanks to Baiser having nurtured them all into better people in the first place, it would've stopped the mascot's evil plans and finished up every storyline neatly.
The magical girls would have won, the bad girls would've probably buried the hatchet, the evil mascot would've been stopped and Baiser herself would be content having played her role to perfection and probably even survived to become friends with the magical girls as just a normal human again.
So yeah, I can't fault anyone for expecting this encounter to have been the finale. They were literally on the last remaining plot threads.
All of this is baseless speculation on your part as we still dont know about the extent of Baiser's powers. And no most of the story threads were not resolved. Girls used their La verita forms for like one or two times after such a long time building them up. If it ended here it would be suppremely unsatisfying. And we still dont knlw shit about mascot characters and their motivations. Baiser and Leopolds relationship,, Alice's new form if any. Frankly anyone who was expecting it to end here wasnt reading properly.