It is, but it's a use case that has a shitload of money behind it.
Do you know why we have had reliable e-commerce since 1999? Porn websites. That was the use case that pushed credit card acceptance online.
The demand is so huge that firms would rather stumble a bit at first to save huge amounts for a bad but barely sub-par UX.
For vanilla FF I use multi - account containers, uBlock, and privacy badger.
For other FF forks like Librewolf, I get more blocky, like JShelter, a random agent switcher, and if that breaks a site beyond use I try Chameleon and NoScirpt.