We want him to have actual motivations and reasons for doing the things he's doing outside of pure vanity and jealousy. The Makuta of G1 and G2 is completely 1 dimensional, he's evil for evils sake and behaves as such. Yes, we want him to be morally grey, but he is also still our villain.
He has reasons for doing what he's doing and truly believes what he's doing is right for everyone, and that's what makes him a grey character. Through his actions and interactions with other characters. He is not an anti-hero, and he doesn't need to be one to be a grey character.
The suffering caused to the matoran through death, pain, and loss are all creations of Ekimu in Makuta's eyes. He's the one responsible for making them suffer, Makuta merely wants to free them from the mortality they've been forced into by Ekimu.