No, it wasn't a coming of age tale. Gurren-Lagann is a "memento mori" take on the concept of progress. The quirks of the classic "coming of age" tale such as honoring your legacy, change, breaking traditions, reciprocal individuality or burden of responsibility were only used as a way to bring this idea to a more personal level.
The show is just an unholy cross between silly mindless adventures such as GaoGaiGar or G Gundam, the subversive storytelling in Evangelion and conceptual, surreal narratives like Mind Game. This is basically the best way to describe it, really.