This show and Kill La Kill to me are shows that you must not take at surface level. Gainax have been doing anime for more than 20 years. They were anime fans when they started and watching Gurren and Kill La Kill, it's obvious they still are. Nowadays though, they have the proven talent and can command the budget they want. At this point, they are just taking the piss at every convention they can think of and doing it with a level of talent few have. If you compare Gurren to Attack on Titan, the satire is even more obvious.
It could almost be said that the lack of animation is a nod to the earliest animes that were just a series of manga slides on screen. Obviously, it's because it's cheaper. But watching the barely animated KLK, I couldn't help thinking about the old old old anime.