As a couple other folks have noted, I think the fiat on ramp is a big hurdle to solve. We do need simple purchase with credit card options directly on-site.

More than that, Patreon is similar to other crowdfunding, like KickStarter, with a focus on backer rewards; frequently physical, or at least digital items delivered direct to the recipient. (Coupon codes, high resolution art files, exclusive download links, etc.) There almost needs to be a hybrid system at play of a centralized website + blockchain finance. I’ve found a project like Fundition to be inadequate for a broad campaign precisely because there is zero way for me to gain information on my backers and reward them accordingly.
This is another obstacle I believe needs overcome. There has to be a toolset for creators to manage their subscribers. Patreon would be much less used if it relied only on the kindness of donors hearts. Systems need to be in place for secure collection of names, emails, physical addresses... whatever the consumer is willing to leave. The masses don’t want to donate anonymously. They want that fun care package in the mail!

Can that be achieved all “on-chain” in a decentralized fashion? I don’t know... It’ll take work on encrypted memos & messaging systems and some interfaces to make sense of all the data if it’s to be kept between the two parties.

Without that, it’ll basically be Patreon with an option to pay in crypto. There will be a centralized site handling customer data. They will take fees to cover costs. They will block projects from being seen or receiving transfers through their system based on the laws in their jurisdiction, etc.

It’s something I’d love to see well implemented, but it’s tricky all around.