I bought the og game maybe a year or so ago and came back to play once I learned it got a big update/reworking, but this page says I can't download it now for some reason?
You can still find it in your library or on the page at the top you should see a message from Itch that reads "You own this game" followed by a Download button. Click that download. That will take you to the page where all the version releases of the game are.