Patreon has three membership plans for creators, none of which are actually 10%. :) The basic one is 5%, the "pro" one is 8%, and the "premium" one is 12%, which is targeted more at companies/teams than individuals. (It comes with a dedicated account manager and I believe some kind of shipping/fulfillment system for physical merchandise.) Their payment processing fees are also actually lower than what you'd pay Stripe directly for pledges of $3 and under.
Patreon isn't problem-free, but I think they get dinged a little too hard by folks sometimes. It's not very easy to find a competitor that offers comparable value-added services at significantly lower cost.
Online payment system is typical platform business where network effect dominates.
There are multiple competitors for Patreon, but they can't get off the ground because they don't have the users because they don't have the creators because they don't have the users.... You can build much better platform and it's just crickets in the sales because operating costs on smaller userbase are higher. Small competitor might force Patreon to reduce prices a little until they can kill the competition, but it's hard to have stable competitors.
Businesses that already have massive number of customer subscriptions and brand recognition could enter the market.