Is a Dyson vacuum cleaner generic, because other companies have started making similar models?

The design has become generic, yes. That's what generic means: "pertaining or appropriate to large classes or groups as opposed to specific."

So when everyone starts copying the design of this Facebook page, the page will become generic? I somehow doubt that’s what parent was alluding to. I read ‘generic’ as an euphemism for ‘unoriginal’, which Apple product pages definitely aren’t.

Yeah I think this is much nicer than an Apple product page.