I definitely can see that you could expand this game further into a full game!
The main mechanics of placing blocks is nice on its own, it's like a puzzle thing, and I don't know if that's what you are trying to go for but I feel it could get kinda dull if that's all their purpose. I'm sure you have something in mind but I can see they serve a purpose of like stopping the heroes from invading your realm or something like that.
Also like others have said, there's a lot of info dump for this type of grand strategy game so if you can make the onboarding process feel smoother, I think it could be more well-received.
But anyway, I do see the potential here and I wanna see where you take it in the future :)