...so why does this dev keeps this awful system where you need to start over each new version ?!
The fact that the Dev changes the
content of previously seen events/scenes, the
order that those events/scenes can occur in, the
trigger requirements of those events/scenes, and the structure/naming of the game's variables all contribute to the reason why old saves become invalid and why the latest release becomes corrupted when old saves are loaded.
(a 'save' stores more than just the current (at the time the save was made) values of all the game's 'known' variables.)
For this particular release it didn't help that the Dev also had to make changes to the game's content to suit the requirements of Patreon, thus even if the game contained functionality that could convert an old save into one that was valid for the current release it would of still been likely that we would of needed to restart.
Please remember that we are playing (testing?) 'beta' / Work-In-Progress releases of this game and not a 'final' release, so it stands to reason that there will be changes that force a restart. The need to restart also happens when alpha/beta testing commercial AAA game titles.