you bought the game once, as a customer you wish to receive complete features, polished experience and a fully playable mechanics.
The patreon is just an option to give us extra support and donation, in exchange as gratitude we open some early features for the donators. The so called futa mode is still a WIP mechanic and is not even fully finished.
Plus its just some bonus content behind patreon (not much of it so far is actually patreon only), which is what so many other studios do around with even worse paywalls.
You buy game on itch once, patreon people pay each month, then at the end of month you just receive updates for free. In terms of funding the game patreon is our only secure tool especially nowadays when all paid NSFW games got deindexed, we barely earn anything from itch io now.