Are they? There was a big surge during the pandemic lockdowns, as there was for all kinds of PC stuff. When that ended, sales dropped off, it effectively pulled forward a lot of future demand. Now we all have a lot of still fairly new stuff that's entirely adequate for our needs.
They are no longer viewed as a growth company/stock. Their growth has slowed to around 2%, and they are trading at a PE of 37. New product releases are underwhelming. Berkshire sold most of their Apple holding last year, a good indicator that the growth isn't there at these valuations.
I think the author's main point is that it's product revenue is flat (iPhone) or dropping (all other products), in comparison to (I guess) other tech companies that are still growing.