I thought that the lack of difficulty (that must exist in any strategy game imo) was the only problem here, but I played the game for a few hours, finished it, and expected to see at least an ending screen, which I didn't.
i had to replay the first levels a lot until i got near the second guardian, then i stopped needing it and now i'm near the 4th guardian.
usually, it makes more sense to need replay when i'm near the end, but i can live with it.