@Latecomer
FiM already did the ultimate magic battle thing. And every EqG special, besides the summertime shorts and Holidays Unwrapped, always had a personal relationships component.
The writers (and hopefully I’m not the only audience member) are more invested in the characters than some new baddie. The question of if Sunset would take an out of state scholarship, leaving her friends behind, is more interesting than “how long before the girls laser this person”.
I mean, you could have the real Grogar show up, turn all the previous baddies evil again, including Sunset and Sci-Twi, and have a giant battle but it’d be all spectacle and no substance.