I think this is largely due to the fact that Mage Knight is one of the few (only?) games that actually plays best solo. I actually think that Mage Knight is pretty strong if you want to play a highly complex solo puzzle game.
Road to Legend is pretty good for solo Descent, I have also played a game or two of Zombicide solo and thought that went well too. I'd stay away from the D&D "Ravenloft" games though, since once you figure them out they lose any real interest.
I think if I really wanted a solo game I would look into the MoM 2e game. Not only does it have an app, but it also tells a story which for me helps keep me engaged. I've not played MoM 2e (I have 1e) yet though, so this is all based on second hand info.
Hope you find something fun!