I don't know how to feel about that. On one hand it makes sense because Cersei is the one who has the developed backstory and we can get a really emotional ending for a bunch of characters.
Cersei is also so evil that she's worse than the Night King, who is just a rogue A.I created by magic.
Cersei also has a human side, as seen with her love for Jamie, but she's also tragic in her own way.
She is a fitting villain, and mirrors the mad king well enough. But for all of that, she just doesn't have the power that dragons or the undead have.
She can trick and scheme, but Dany and Jon have to be pretty dumb to fall for her any of tricks.
On the other hand, the Night King is too meta. His story is supernatural, and also divine in the roles that the God of Light and Dragons play. He also compliments Jon's story arc better.
I can't see the show having Cersei in the end because her battle would have to be between herself and Dany.
But the entire series is about the Starks and the White Walkers, so Jon/Night King has to be the ultimate fight.
But the ordering makes that difficult since we can't possibly have the entire season be between the dead and Jon Snow.