Adult content is 20% of Patreon's bottom line. So actually, at 1/5 of their earnings, I'd say plenty of people are willing to pay for it, and it is plenty of money.The problem isn't earning money on an alternative platform its convincing people to trust you, the new guy, when Patreon already exists. To put it in perspective, you have to think about being a small business owner in a 1 walmart town. Do you try to compete with walmart directly? Or do you offer something walmart doesn't? Put simply its not possible to compete directly with walmart, They'll operate at a loss until you're out of business. So what you do is offer something they don't.
In the case of Patreon, you offer a platform that is free of censorship, and you find a funding mechanism that makes that possible. I hate to say it but there is one, and I hate that it is this, but cryptocurrency doesn't give a rats ass. Its largely untraced and available to be purchased and used as you see fit. It would make it possible to avoid the issue of High Risk as well. You don't have to show your wife what you bought with the bitcoin, so all she knows is that you bought bitcoin. It wouldn't be as popular as Paypal, there are more steps involved, but it would allow anonymity, not show up on your shared credit card as whatever smut you were buying, and it would allow the creators to create whatever they want.