I think people sometimes approach the "evil route" too narrowly. As in, playing the evil route means you have to choose the most despicably evil option at every opportunity. Then it ends up being very cartoony murderhobo.

But it is perfectly possible in BG3 to help everyone and gain their trust and support and turn around at the very end, dominate the elder brain and enslave everyone. The game allows for nuances and morally gray if you wish to play that way. You can sometimes help people for personal motives and at other times sell them out because it fits your purposes. There are many variations of game states in the end that sets up a world with both good and bad consequences depending on what you decided to do with the elder brain, crown, Orpheus and various other personal choices for the companions and dark urge.