Isolating experience would be ok if you played as an unhinged murder hobo, but logical and charismatic villains tend to end up with a gathering of people who agree with their views, follow their command and want to see them succeed. You can side with Gortash for example, but then the game railroads you into a specific outcome. Larian just took a shortcut, probably due to lack of time to develop the game, and now they're saying it was always intended to be this way. Sure... It's easier to just give you extra fights, instead of creating meaningful content with new companions, storylines and alternative outcomes.
The ending of the game itself is proof of them simply not wanting to develop the evil path. The good ending is longer, has an epilogue, a newly added party. The evil one got nothing new. You also don't have a way to be villains together with your LI even if that's what they ask of you.
