I honestly like everything here, except for how you rendered the pushcart, since you have some hard banding there, you should make the second brow shade AA strips shorter on the bottom of the angled beams as you did on the top, avoiding having pairs of 4 pixels wide clusters vertically aligned.
As for the houses, I really don't have anything to add and I think they are very nice. I see no problem with the blue roof. Perhaps you are reading it as detached because there isn't a larger shadow beneath it like with the other two houses, but I wouldn't change what is working well. The houses do seem made of different materials, but they all look to be fitting in the same style to me
If I were to nitpick, perhaps the horizontal boards on the bottom of the middle house could be shaded differently than just a rectangular shade all around their shape. The same could be said of the horizontal suspended floors of the first house, and the fix would as little as pushing a few pixels on the extremities to avoid making the shadow hug the outline on the sides.
I love the palette and its clean use here by the way.