Not dying, just changing.
The biggest change is that collectors are much more sophisticated these days, so fewer are accumulating stamps torn from envelopes or sheets of postage directly from the philatelic agencies.
The quality of exhibits at stamp shows is way better than it was in the 20th century.
Another change is that it is attracting more women than men, both at the childhood end and at the retired end. (One gap for both genders is that people tend to stop collecting stamps for a couple of decades when they hit puberty and discover sex. They return after the kids are in university.)
But yes indeed, there is a lot of discount postage available on eBay. (*cough*)
And the Dominion of Canada has never demonetized any stamps. In fact, the stamps of Newfoundland are still valid for postage on Canadian mail.
