Doing the money order thing is so inconvenient these days that 90% of consumers will just skip you. It's simply not practical.

Sounds like they just need to pull themselves up by their bootstraps and work harder.

They could also accept checks via the mail. Or cash via the mail. Or cryptocurrencies. Or gift cards. Or barter. There are multiple options available to them.

Those things are all really inconvenient.. Really, who wants to go out and mail something and wait for it to arrive? And gift cards risk the same kind of banning of credit card companies. This is going to limit any business beyond inviability.

The only thing you mention there that is a serious alternative are cryptocurrencies. And those are constanly fluctuating, needing very complex hedging against sudden value changes. And still something that most consumers will really struggle with. Most will not have a clue how to obtain crypto or how to deal with it (safely).

It might work for a really highly educated niche, but not for 99% of consumers. They just want to put in their paypal or credit card details and click buy now.