Just an aggregator of on-ramp services, not a real merchant system. Not good for conversion rate or user understanding because it cannot be iFramed and users are confused when sent randomly to a page to buy crypto to an unknown wallet with no info about the purchase. And you are right that crypto on-ramp is less likely to go through than other card purchases; this is mainly due to the MCCHave you tried https://paygate.to ?
It works if your users are informed in advance what they need to do and not to change anything etc. but unlikely you would have a business where that is true