I’ll go against the grain and say literally all of it. Every piece of technology that exists is a compromise between what the designer wants to do and the constraints of what is practical or possible to actually pull off. Therefore, all technology “fails” on at least some metric the designer would like it to achieve. Technology is all about improvement and working with imperfection. If we don’t keep trying to make things better, then innovation stops. With your example of VR, I’d say that after having seen multiple versions of VR in my lifetime, the one that we have now is way more successful and impactful, especially in commercial uses rather than consumer products. Engineers can now tour facilities before they are built with VR headsets to see design flaws that they might not have seen just with a traditional model review, for example. Furthermore, what we have now is just an iteration on what we had before. It doesn’t happen in a vacuum, people take what came before, look at what worked and what didn’t, and what could be fixed with other technologies that have developed in the meantime. That’s the iteration process.