You know what the error message means, you've decided to use a non-fully-featured browser to visit their webpage. It's like taking the wheels off of your car and then complaining that your immobile vehicle isn't eligble for the drive-thru lane at a restaurant.
They have a print edition that you're welcome to buy from any local store that sells newspapers.
I'm sorry, I'll tell Mozilla that Firefox is non-fully-featured right away.
HN doesn't seem to mind it, I don't see why showing me a bunch of text is such an insurmountable technical challenge for a website.
Also, to continue the car analogy, it's more like turning your headlights off and the drive-through complains that your car is nonstandard and won't let you order.
Why would you tell Mozilla that? Their firefox browser works just fine with WSJ, both to display articles and to subscribe to their digital offerings.
As is nearly always the case: the user is at fault.
To fix the car analogy that you maliciously broke, it's like a car that you took the engine out of, and then complain that it doesn't drive. But if anyone asks why your car is broken, you weirdly pretend that you didn't take the engine out of it, and make asinine statements about how "it has wheels, why doesn't it roll" knowing full well why it doesn't.
They have a print edition that you're welcome to buy from any local store that sells newspapers.