Don't be silly. This has always been a free game so there was no obligation to stick around. Even if it IS really nice to see you come back.
Honestly? I'd say just stick with AI. The sad truth of the matter is that "good enough" pictures done by AI are a great way to flesh out a game like this. Excellent art is nice and helps elevate the content... but if there's 3 or 4 times the amount of stuff then it really does need to be excellent. It's a huge burden on you the creator when you're doing everything.
I came to this project knowing it was AI. I'd be happy to see it continue as AI, or I'd be happy to see something new. I don't really have strong feelings one way or the other.
I also wouldn't mind if you wanted to do things with proper 3D models, but that's a lot of time and effort and you've been scared off once before. So I don't know that I'd want to push you or anyone else to commit to that.