Pakl said:
Broly was not brought up in movie 9 actually proves my point. Movie 9 was based on the Cell Games and there was a progression of the Z fighters power like in every movie.
That's an assumption based on theories about Movie 8's timeline, something which no official sources have verified (beyond video games placing it prior tot the Artificial Human battle, which simply isn't true).
In movie 10 however, only Gohan who was weaker was used and the kids. There was no progression so they brought Broli back because he was popular. Why not bringing him back in movie 10? It was both because there was no progression in the stroy and because Broli was popular.
It's because Broly was popular, yes, not because of a lack of progression. A lack of progression doesn't limit what villains can be used. If anything, it would add more reason to do more than bringing back a previous villain stronger than before.
In movie 11 he was brought back too brcause of the same reason as Bio Broli was a weakling anyway.
The same reason in that Broly was popular. If power progression was a reason, that would add more reason to use someone other than Broly as Goten and Trunks had become no stronger than someone who could stomp them without his strongest form and Bio-Broly presents so little traits he could easily be replaced with just a generic monster. Popularity was clearly the sole reason.
Koyama also bluffs a lot about Broli when it comes to strength so I would not take that seriously.
Official statements still hold more weight than assumptions, and Koyama saying he couldn't come up with the idea of a foe stronger than Broly is clearly not meant as a joke.
Just like it disproves the idea that power progression is the primary factor in creating new villains.