How do you even justify product with Apple's poor plans? Besides, AR/VR itself is extremely niche.
Well, yes, it is niche, and there is a niche market for it. If you're not interested, no-one forcing you to buy it. SDo ignore it. I have no interest at all in buying one.
But R&D is worthwhile. The amount of patients Apple filed during the development process has itself a significant value as IP. And, as the example I gave, a lot of Apple's first gen products, even if they themselves are not particiularily popular, are not thrown in the bin by Apple. That would be wasteful. The technology gets repurposed.
The hand tracking technologies alone have value. These will be reused in other product ranges.
Remember that the tech industry was generally negative about the first iteration of the iPhone. See how that turned out. The original iPod's initial spark came from Steve Jobs looking at Firewire, a technology Apple had already developed, but wasn't using overly, and wondering how this technology could be exploited for other products. Apple bought almost all of Toshiba's 1.8" drives long before there was even a design for the iPod. The same drive made the initial MacBook Air possible.
The haptic trackpad was developed for the 12" MacBook. Now it is standard across all MacBooks. Audio improved significantly on all Apple devices after the 1st gen HomePod was developed - because they took what they developed in that project and applied it to other products.
Technology and IP gets reused. Irrespective of what happens to the Vision Pro as it is now, the results R&D itself has quite possibly already made the Vision Pro project worthwhile. I'd also guess that a lot of R&D done during the cancelled "Apple Car" project crossed over tot he Vision Pro, in terms of camera tracking. Product ranges are not hermetically sealed in their own little bubbles.
Looking at all of this, the Vision Pro project has not been a massive failure in the way that "Apple Intelligence" has been so far, even if the Vision Pro headset hasn't sold a massive number of units ( it was't necessarily expected to).
Marketing of the Visio Pro was problematic, purely because 1) until the Vision Pro, headsets = gaming, and Vision Pro was very deliberately not marketed as a gaming device and 2) there's the fundamental problem of headsets - it's very impressive technology, but for a lot of people, it doesn't really add anything significant over working with a big screen when sitting at a desk and just getting work done.
But none of that reduces the value of the technologies developed, which will be reused in other devices. AirPods for example.
Denying. that just because you don't like the current iteration of the product is a little bit blinkered.