I realize that there may not be any privacy problems depending on how it's implemented, but I'm still not interested; it's using a creaky centralized system that is otherwise on the way out
Just an observation.
People would sooner or later use centralized solutions
or formulated more properly: less decentralized solutions. It is a matter of time until the merchant prefers to receive their sats by only giving an email instead. It'd a benefit for their customers.
If they insist on the decentralized ideology and also want from their users to send sats via email, they could setup their own email server and be at none's dependence.