Some close to credit card options Paygate, Payblis, (multiple on-ramps) and I found this one luxfintech.com which is being used a few AI porn/undress/Face swap websites and some porn websites like Faphouse (accepts CC/Debit via base, Venmo and Paypal). These provide as smooth a process as possible for cypto newbs to use Fiat onramp without you having to send them a link and wallet and explain what to do. Also these services have API to integrate into the checkout process. All the customer has to do is Pay with most of the onramps having no signup or just an email signup to pay. From what I can see, these services have webhooks/api setup to redirect customer to the best onramp based on their country and the amount they are spending. Then, they generate random wallets and pre-fill it in the onramp form. Then monitor whatever wallets it's sent to for confirmed payment, and customer is redirected back to whatever link you have set. The money is then sent to your polygon usdc wallet. Based on their setup, it's something anyone could setup themselves if you have some coding/webhook knowledge (or use AI). Then cut out the service and % they charge.
With that said, some customers may need to KYC if they are directed to a certain onramp and are at a certain spend level. Then another risk is hoping these companies don't run off with your crypto and continue sending the instant payments to your wallet.