so this is one quarter answer, three quarters case for it to come back. i think its still worth a read.
My guess is the impending release of lazer. Sure, lazer has been impending for a very long time now, but its development is not stagnating in the slightest.
Another reason is that Aspire V didn't really turn out the way people wanted, either for onlookers who didn't like the results, or for the people running it seeing its backlash. I can imagine that making potential hosts hesitant to revive it. I still look back on that competition very fondly for Aspire mapping as a whole. Many of the maps created were more memorable than 2018's crop, and the more exceptional of the bunch prove that there is plenty more for the Aspire scene competitively. To add onto lewski's point, there's definitely a long forming trend of visual spectacle, but that isn't mutually exclusive with quality. I will always believe that the contest still has the potential to generate maps as esteemed as Monstrata and ProfessionalBox's entries.
And yes, of course there's not too much new being discovered. But outside of Aspire maps, ranked maps are far from dead, and its not like the base game has gotten anything new to play with. At least in my opinion, that's already a good case for another competition. Also, it's not even really the case that there's nothing new to play with! Slider tick art, quantum sliders, and picturator sliders are all things that you may have never seen used before. Well, you've probably also never heard of them, so it doesn't exactly count. Just bask in the silliness of their names.
I would be happy biding my time for lazer to drop variable AR and CS, and then base the next Aspire around that. That said, I would be incredibly happy with another contest, hopefully made in a similar vein as Aspire V but with less category bloat and a mapper's pick. Yes, I do just really want to try mapping in one, but I also think there is a lot left to say before lazer rolls around.