I want to be honest: I am not a fan of Tetris, but I want to make it a fair feedback :D I am a fan of your approach and the minimalistic design around it makes it a feel quite good. Some scene transitions looked a bit weird. The level loaded a bit later than the new shape. But hey, in a 48h Jam game, those things are normal. I would have liked it if in every play through one had only a single shape to point the jams theme out even more. But then it would be less fun though.
PS: Of course I would like your rating on my game as well ;) https://itch.io/jam/gmtk-2019/rate/460633