The anime adaptation looks like it's probably never gonna be finished, and I heard online that it's been fully translated. However, when I tried reading it on dynastyscans, mangadex, and vymanga, but none of them had the whole series. So anybody know where I can find it?

The most probable reason is that the manga and light novels are already licensed in North America so no freelance translation group wants to touch this.  I believe Seven Seas Entertainment has the right to the series and they should have this available for purchase here: I’m in Love with the Villainess (Light Novel) | Seven Seas Entertainment