Very nice!
My initial reaction is: it's not giving me the piece I want. It's trying to force you to clear individual lines as soon as it is possible to do so. But in real Tetris, you want to clear four lines at a time to get double score, which may mean withholding a line clear when you could have done one.
Consider this replay: హටເח௨ඞܗТۑටܢݹ௫੬ຽߢ௧ලບঅযلЈǶ
It ends by giving me nothing but S pieces, because it wants me to take the single line clear. It won't stop giving S pieces until I do so. In actuality, any other piece would be preferable; there are available spots for all of them, and I can build up to a Tetris. But with the S piece, my only options are to sacrifice the Tetris for the single line clear, or create a hole in my stack.