My vibe is that you actually don't like MSpaint better, it's that you were simply too lazy to try anything else.

If I can't tell any theme from a couple of tiles, there may be a problem. I can make two tiles and there's already a clear hint of the theme. It's barely to do with drawing quality, it's what the tiles are trying to convey. Top secret may be one of those tilesets with tiles that convey nothing other than being just blocks, however it is not a good example on how to set a theme.

Being new doesn't make you immune to critique. If anything, it helps you develop your skills faster if you learn what to improve on earlier. I don't usually review casual artists, though since it was a contest entry, I felt inclined to.