As other posters have commented here, glTf is the current best practice for runtime delivery formats (and, by extension, glTf would be a terrible choice for author-time DCC Data exchange, for exactly the same reasons as why USDZ is better suited to authoring than delivery).
Moore’s law and computers getting faster won’t make USDZ a good runtime format. glTf will remain the better runtime format and USDZ will remain the better authoring format, because that’s what they were designed to do well. As someone else observed, it doesn’t matter how fast your browser gets, no one is going to recommend you populate your website with PSD images, because PSD is an authoring format not a delivery format (and likewise PDF is an equally terrible authoring format but a great delivery format)
1 - look at the people onboard the USDZ format (pixar, adobe, autodesk, epic, etc.). This is geared towards getting designers to bring in high quality 3d from the the first step of the pipeline.
2 - Just because apple uses the format doesn't mean they don't optimize it for display. I have no idea what happens behind the scenes, but if they could make PDF work well for a desktop, then I have faith in them. Look a this link [1] and the video [2] from a YEAR AGO. It seems to support my thoughts (via the Unreal Engine). The second paragraph is the key.
I understand your concerns, but I truly believe that in two years, you will look back on this and say, "yeah, they figured out how to get this to work well." Of course, I am wrong occasionally, too :)
[1] - https://www.cinemablend.com/games/1631230/why-two-disney-fil...
[2] - https://www.polygon.com/2017/3/1/14778602/epic-gdc-finding-d...
The example you given is actually irrelevant for consumer use cases. For consumers, loading speed matters. They are interactive apps. They can't spend too much time loading. While for film studio, they are batch rendering scenes. Loading speed is a lot less important.
That is technically true, but in the same sense ENIAC could have rendered Toy Story. Realistically there's a lot more to it than just transistor count.
It's also a strange comment, because in all three cases (the original render farm, iPhone, or ENIAC) it would (or did) take months of real time to render the whole thing.
If you look at another technology that started out on the pro side and eventually dominated the consumer landscape, it's Adobe's PDF format.
To quote wikipedia (sorry): "In the early years PDF was popular mainly in desktop publishing workflows, and competed with a variety of formats such as DjVu, Envoy, Common Ground Digital Paper, Farallon Replica and even Adobe's own PostScript format."
I think those key words suggest that Apple is being farsighted here. In 10 years, the idea that computers will want anything less than a professional model will be quaint.
Remember, your iPhone now has the power to render Toy Story [1].
[0] https://en.wikipedia.org/wiki/PDF [1] https://twitter.com/ID_AA_Carmack/status/766989221961748480