The under-30s increasingly care about climate change and other more immediate threats. Unless they have Type 1 diabetes, blood glucose is not an issue for them.
Apple under Jobs did a solid job of making cool lifestyle accessories for all ages and genders.
Apple under Cook has drifted towards a kind of white picket Disneyfied techtopia, where the sun always shines, people always smile, everyone is very creative and colourful but also professional, fit, and focused. And it's somehow very sterile and boring.
As a result Apple missed out on the user-generated content wave, which was owned by YouTube and then TikTok. Apple already had some of the basic infrastructure in place with podcasting, but a middle aged outlook meant it missed the (mildly but interestingly) anarchic possibilities.
And that's going to be a problem for the future. Jobs was anarchic enough to want to shake things up but stable enough to make the shaking work (mostly).
Cook is small-c conservative, safe, and suburban in outlook. And now Apple is too.
Asking what The Next Big Consumer Thing will be is already missing the point because it assumes a model where there is a Next Big Consumer Thing and it's important enough to matter.
Ten years from now that's going to look like a weird and dated assumption. There will be much more chaos and uncertainty, and I suspect Big Consumer Things will be less important to everyone than they are now, and the people who are in their 10s-20s-30s now will be looking for something entirely different.