Okay... that's still... really annoying, though. I was already at the very end of the last version, and even if the new version is sped up, it's going to be very annoying to have to do everything all over again. Why couldn't you have added an option to skip to where the last version left off, prefaced with a few selection options, to let the game know what (game-changing) choices a player had made in the previous version? Lots of RenPy games do that, especially whenever such a save-conflicting update is made.
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The code is different and has different choices with different consequences, compared to the old version.
That solution you propose would only work in a linear game, but in LP you can progress in the order you want, with the girls you want and there are some choices that remain between save games (even if you start a new game, that choice persists). Less than 5% of the total content is mandatory and it would be a titanic job to track all that progress for each player's save game.
However, there is a complete save file (with standard choices) in the discord community, if you don't want to start over.