The setting of the background applies to the Water Margin, which also adds some spoof to the story. Moreover, there is a lot of investment in animation production. Therefore, it should be a relatively sophisticated work in the 90s.
However, one thing that stings me is that the title is suspected of fraud. Under the guarantee that each episode lasts at least forty minutes, it does not make people feel that the whole story has any intuitive connection with the giant robot. Tbh, even removing the hero and his robot doesn't seem to affect the story much, because they are not the center of the story. After realizing these things, this well-made anime started to frustrate me.
Of course, I am very interested in Yokoyama Mitsuteru, the author of this series, but I can't deny that GR is a bad start to getting to know him.