@PkmnTrainerVIt already happenened.
Ultranecrozium Z is just a means of transforming into Ultra Necrozma in the games, but in the anime Necrozma already transformed without the Z-Crystal. It might not even exist in the anime.
It would be a pleasant surprise if we saw Necrozma again, but expecting it isn’t the way to go imo. They need to promote LGPE, not USUM now,
I know what you mean. But if you recalled Lillie story during in her own sleeping bed story that passed down from her grandfather to her mother and now to her in episode 87 at the start of the Ultra Necrozma Arc. Blinding One cannot generate it light by it own and will lose it if it overused it power too much and become black with the broken body again. I highly doubted, Blinding One will lose the light again. Despite, everyone in last episode sharing their own light to Necrozma. At the same time, they promoting the LGPE, they have to showed the remaining of the Z-Move (19 total) that haven't yet debut into the anime as we have 48 episode left.
But hey, the next episode already going to showing the Catastropika by the character of the day with her shiny Pikachu. Which is a great start, but I wondering are they going to rush THIS one, then it will be hilarious bad again like they did with the Aether. I hope better not, keep our finger crossed.