After showing up 9 hours later than expected, I finally got to play Shredder's Revenge and:
The game meets expectations. So far I've played with Michelangelo, because he's my favorite Turtle and a bit with Leonardo because I love Cam Clarke... after 35 years, listening to the OG Turtles is a bit bizarre yet amazing. I haven't fully played it because it was available far too late instead of midnight.
The game is a 90s styled Beat-em Up game with modern elements like Super Moves. If you're used to Konami TMNT Beat-em Ups, you should feel mostly at home with the game.
It seems Casey is an unlockable for beating the game... not sure if the requirement is The Story Mode with 1 character or all 6... or if it's unlocked through Arcade Mode.
Unfortunately, I won't be playing much due to some physical pain issues. In any case,if you love Beat-em Up games, get Shredder's Revenge. Doubly so, if you love TMNT!