Don't throw factual numbers at me, you pompous top hat tea sipper!
Although to be fair, I think GR being a morning kids show also gave it franchise advantage over a simple OVA series. For Unicorn, DVD/BD sales would be everything, whereas Gurrent Lagann had a whole franchise of goodies.
Anyways, I agree that compared to the 80s, the golden age of mech shows, it's been a declining road.
The end of the Yuusha series in the 90s also had a large impact, especially in lower age bracket markets.