Well, there are technical aspects which can be overcome but sometimes an old save wouldn't also make sense anymore if the story and/or mechanics change. Add a new stat - what should you use as a value for some advanced player? A storyline has been broken up or fused so the point the old save was in just does not exist anymore. Place where you are has been taken out completely. (This is generally speaking, not all of it applies to this specific game.) So sometimes an "import old save" wouldn't work.
Just one of the risks of following a game in development pre alpha - nothing is set in stone. Even more so, the more gameplay is involved instead of "just" telling a story. It is different from playing a game and then having content added through DLCs or similar. I hate redoing stuff as much as the next guy, but it is a risk I am willing to take for the experience of watching the game grow. It's a personal decision whether you prefer it this way or want to wait until a game releases. But I guess you cannot have your cake and eat it too here, at least the risk is there.
I agree on this when the game is changed "a lot", for example when a grinding system is added where there was none before. But here, we already had the grinding part - was annoying enough to get all stuff with so poorly paid missions - and a free roaming part.
The problem is more tied to Python: such breaks are way too frequents with Python-based stuff. And while Ren'Py
COULD have handled that, it doesn't and it's annoying too. That's why I spoke about an external tool: you use it simply to import the old save, complete the missing parts either with mean values and/or by asking questions and you save the converted file ready to be used.
But you need framework's assistance to do so, at least by having a "save" module with all variables. To be honest, I still don't understand why - while a savefile is a compressed archive - there is still a
binary file as main data... It could be an XML file, or a JSON, but no: it's a freaking binary file, the thing that pollute computing since computers are a thing.