I wouldn't say it's an age thing. Plenty of modern stuff comes very quiet, especially on the lower-end. And the loudest freewheel in my stable is from 1979.

The amount of noise a combination of how they're configured and how they're lubricated. Thicker lube can quiet the mechanism somewhat, reducing the spring tension on the pawls can also do it. You can even reduce the sound by removing pawls from the freehub if you really want to.

But lots of people want a loud freehub. Much in the same way that the hum of high-performance road tires is desirable.