Haha I feel like VR has already found it's niche!

Apple taking over an entire car with car play ultra or otherwise comes to mind. Latest Aston Martin model with car play ultra was atrociously laggy, ran instrument panel screen at like 12fps.

ai

I'm long-term bullish on VR, if you mean having a HMD designed to provide an immersive 3D environment. Like, I don't think that there are any fundamental problems with headsets, and that one day, we will have HMDs that will probably replace monitors (unless some kind of brain-computer interface gets there first) and that those will expand do VR, if dedicated VR headsets don't get there first. Be more portable, private, and power-efficient than conventional displays.

But the hardware to reasonably replace monitors just isn't there today; the angular resolution isn't sufficient to compete with conventional monitors. And I just don't think that at current prices and with the current games out there, VR is going to take over.

I do agree with you that there have been several "waves" by companies trying to hit a critical mass that haven't hit that point, but I think that there will ultimately come a day where we do adopt HMDs and that even if it isn't the first application, VR will eventually be provided by those.

Encryption with unexploitable backdoors.

Flying cars.

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.

The hype around biotech. It has been around for 40 years, and the next big thing is just around the corner, but progress is always much slower than all predictions. Nuclear fusion will be available in ten years time; I’ve heard that in 1970, 1980, 1990 etc etc. Conquering the solar system, the universe - perhaps in 1000 years?

So I have a contentious one. Quantum computers. (I am actually a physicist, and specialised in qunatum back in uni days, but now work mainly in in medical and nuclear physics.)
Most of the "working": quantum computers are experiments where the outcome has already been decided and the factoring they do can be performed on 8 bit computers or even a dog.
https://eprint.iacr.org/2025/1237.pdf "Replication of Quantum Factorisation Records with an
8-bit Home Computer, an Abacus, and a Dog"
This paper is a hilarious explanation of the tricks being pulled to get published. But then again, it is a nascent technology, and like fusion, I believe it will one day be a world changing technology, but in it's current state is a failure on account of the bullshittery being published. Then again such publications are still useful in the grand scheme of developing the technology, hence why the article I cited is good humoured but still making the point that we need to improve our standards. Plus who doesnt like it when an article includes dogs.
Anyway, my point is, some technologies will be constant failures, but that doesn't mean we should stop.
A cure for cancer is a perfect example. Research has been going on for a century and cumulatively amassed 100s of billions of dollars of funding. It has failed constantly to find a cure, but our understanding of the disease, treatment, how to conduct research, and prevention have all massively increased.

The big one would be viable nuclear fusion, we've been trying to figure it out and spending money on it for like 80 years now.

That being said, there's actually a lot of verified progress on it lately by reputable organizations and international teams.

Printer drivers.

Apparently sending data serially at glacial speeds is impossible.

I'm going to get downvoted for this

Open source has its place, but the FOSS community needs to wake up to the fact that documentation, UX, ergonomics, and (especially) accessibility aren't just nice-to-haves. Every year has been "The Year of the Linux Desktop™" but it never takes off, and it never will until more people who aren't developers get involved.

Tablets have had a couple of "waves". They've never really gone away, but also haven't really become the norm, either, not in the larger-than-a-current-smartphone sense.

https://en.wikipedia.org/wiki/Tablet_computer#Early_tablets

cars.

we're in too deep now, investment bias prevents changing strategy

vr is useful but its too wrapped up in corporate bs to really take off for now. its dominated by companies obsessed with ai and by pathetic startups that never finish a product. it just needs meta to be less dominant.

Printers.

Ground-rolling cars as mass transportation. The engineering superb, but the technology inherently can't scale. The storage requirements alone push many cities past the limits financial sustainability, and the spatial requirements for operation lead to massive network congestion as a matter of course. And yet, we keep throwing good money after bad trying to make the system work.

"Smart" TVs. Somehow they have replaced normal televisions despite being barely usable, laggy, DRM infested garbage.

AI, Mass Surveillance and privatization of services people need to live and National security technology

Probably not top ten of mind, but Carbon Capture and Storage (CCS) has been trotted out by the fossil fuel industry for a generation as a panacea for carbon emissions, in order to prevent any real legislation limiting the combustion of hydrocarbons.