There is a reason why the engine was changed, the dev explained it on the discord and it is explained in the game too... The original creator of this game (the one who made the things in renpy) didn't wanted to continue the game, or couldn't... Then, ENNO (the person who does the art) decided to take the game and finish it, but since he didn't know how to use renpy and that he considered that it was too difficult, decided to make it on TyranoBuild instead... That's the explanation ENNO gave
I understand if you guys don't like this change, but have in mind the position that ENNO had... Having to take upon a game and finishing it, knowing nothing about coding (since he was just making the art) and also adding extra-content (the christmas special DLC) completely out of love for the game... Since he's not making money out of it and he also made the game free for everyone