From a UX perspective today, it will always be more cumbersome to initiate a SEPA transfer to the merchant. Some integrations offer a semblance of interactivity with your banking app in an attempt to streamline it, but nothing beats the simplicity entering your cards details or just showing your face to Apple pay. Then from a consumer protection perspective, if something wrong happen with your order or the merchant goes bust, you have no recourse if you initiated a SEPA CT. Card payments on the other hand give you a nice chain of large entities exposing themselves to the merchant's credit risk in front of you.
It can probably work in specific situations (e.g. if you have a niche website with a sophisticated audience ready to overcome the hurdles to acquire your widgets), but for these reasons alone I just can't see SEPA payments going anywhere near even a ridicule fraction of the market share held by legacy card networks yet.