Eh, I can't agree with your "adults were just waiting to intervene" when an entire fleet with thousands of people was annihilated, plus all the victims at the school station. And the ending showed all those kids managing things, whether it's Miorine or Guel or his thicc secretary. The out-of-nowhere "villain" with he massive orbital laser beam was adult, too, ofc. All in all, this anime gave me Persona 5-vibes, "all adults are evil/incompetent" and that's just dumb imo. Again, Iron Blooded Orphans did it so much better, yes, child heroes, but there were plenty of equally competent adults, too.
Agreed with your speculation about a sequel series, some parts at the end definitely felt like a setup for a future follow-up story.
Haven't seen AGE yet, I'm super slowly working myself through the entirety of Gundam, a little over halfway in the first Gundam-anime lol (I have previously watched several newer Gundam-anime, though).
Honestly, I'd like if the next Gundam focuses on some simple, regular pilot with a lowly mechanic-background who finds himself flung into bigger events. No "children only", no dumb yuri-drama, no "politics in the background", just an honest story about a becoming-a-hero protagonist using a not-special Gundam to make do in tough times and building a loyal group of friends and supporters as the show goes on. Gimme pls.