Yep, I agree with this. Although, computers have been generally available at least 20 years now so to some respects it needs to be like any other tool. They got off horse draw carriages for cars. Off of fire for gas and electric ovens, etc, etc.
They don't need to be experts, but they should figure they'll need to upgrade like everything else.
I don't think I'd charge a "tax" or surcharge, but I might make the page unavailable or redirect to a page with links to updated browsers.
But that's how far computers have come in fifteen years
A fifteen year old computer is like a horse drawn carriage, a ten year old computer is like a car build in 1920's, expecting them to do the same job as whats required about tech today is fucking hilarious.
Its like when refrigerators were invented, and ice block producers wanted the government to charge a "Refrigerator tax" cause "It was killing our business" and the government said no, because its how technology fucking advances. If you can't keep up, you are dead to the industry.
Expecting a 15 year old laptop to access youtube is fucking insane, hands down.