Super Mario RPG themed.
The next Tetris® 99 36th MAXIMUS CUP online event is giving you the opportunity to earn an in-game theme inspired by the Super Mario RPG™ game. During the event, collect 100 event points by playing matches in Tetris 99 mode to unlock the in-game theme.
Can I please just have normal Tetris back?
There is Tetris Effect available on Switch, as well as Game Boy Tetris in NSO. Another great option is Puyo Puyo Tetris (and Puyo Puyo Tetris 2).