Divine Dawn is entirely inside of Renpy. I coded the RPG stuff in Python myself, but Renpy handles almost everything visual, aside from some bits I overwrote. I don't know what a visual engine is, sorry.
Not everyone likes the mix of story and RPG, which is part of why I added so much depth but also a lot of cheats, so people could engage with it as much or as little as they wanted. It sucks to see people dismiss it because of one aspect or another, but ultimately that's what the game is and it doesn't appeal to everyone. I don't know if it was the right choice though, this was my first game and not the best start lol.