At least here in Finland SEPA direct debit is usually disabled by default for extra security* as domestic shops do not use it (we have redirect-based bank buttons instead) and with foreign ones one usually uses card instead.

So not really an option of choice in entire EU unless something changes - you don't want to tell your customers to enable something on their bank account first before purchase.

But VISA/MC debit cards are extremely common here, so I guess card+SEPADD might cover most people in EU. Though I think many people here are vary of entering their card details online as they are not used to that (then again, I guess the advent of Netflix and others must've made more people familiar with that).

* IIRC you just need the user's IBAN and consent, and IBANs are not really private as people use them to make payments to each other.