a) I'm pretty sure Gainax were pretty upfront with how TTGL was basically Imaishi's giant love letter to all of Mecha as a genre. There's homages to other shows there, pretty sure Mazinger, Getter and Gundam are included.
b) Counterpoint: Team Gurren's triumph over the Anti-Spiral is the ultimate triumph of the Proletariat over the forces of Reaction, and ending the process of Dialectical Materialism as laid out in Marxism-Lenninism-Giant Drillism.
We evolve beyond the person we were a minute before. We advance a little further with each revolution. That's how a drill works!
The Anti-Spiral oppressed the Spiral races due to a failure of imagination- it simply couldn't imagine a better world. Simon promises to steward the galaxy with giant drill FALGSC at the end of the show, using Spiral power for the benefit of the galactic proletariat.
Edit: Also, Spiral power's not the manifestation of colonialism and genocide- it's the rrrrrrrevolutionary (GIANT DRILL) spirit of the Proletariat as it evolves from national liberation (first half of the show) to global liberation (second half of the show). (Rossiu is a right revisionist who almost derails the revolution with a misguided coup attempt.) That revolutionary spirit is one and the same as the Hotblooded Shonen spirit and Humanities endless potential for evolution.