Similarly to what Hunter Sugar said, it's a lot of patrong gated content.
And while I do think it's probably worth it, It is a bit off putting, I don't know how things have been working as I only just found out about this game but I'm hoping the more content is released for patreons users the more we get unlocked for the free itch updates.
I'll probably pledge money for the extreme version once it's fully completed but until then I can't say I'm not slightly disappointed/put off by the amount of locked content