To preface this, I'm not an expert in it, it's not my particular field, but I do have a bit background than most in adjacent stuff. I'm not by any means up to date in the literature on this though.

Quantum computing isn't a dead end I'd say. While the mixture of the word quantum, long term hype, and lack of big results does tend to ping that "fraud" part of the brain, there is solid scientific basis for it, and there has been small scale systems built for them. The big caveat to that is that they aren't really useful at the moment, and scaling it up will be a challenge.

In a lot of ways it's similar to fusion in that sense. It's vaporware in the sense that it's continually being hyped and still little apparent progress is being made, but it is something that I do think will be achieved some day. That day might be quite a ways in the future, but progress is being continually chipped away at here. Also, for both cases, a lot of the big challenges is in engineering. This isn't like string theory or supersymmetry, where the underlying foundations are sorta uncertain. This is solid science at the core. The question is just of course how to scale it up to a meaningful and useful level, which tends to be slow and very incremental research.

Also like fusion, I think it's something that will be continued to be researched, simply because the potential gains are massive should it succeed. A quantum computer isn't just like a faster CPU. Fundamentally quantum computation allows you to calculate problems that non-quantum computers can't, because the physics of calculation is so different. One basic example is Shor's algorithm. It's an algorithm, a set of calculation instructions basically, that would let you trivially crack one of the biggest encryption setups we currently use. This is an case that sounds bad lol, but it's a relatively easy to see example of how it opens up new computing spaces, some for more positive applications. Most of these applications will likely be less focused on end user aspects. It's not so much about making a fancy GPU for video games, and more about heavy scientific computation.

Capitalists are inevitably going to hype this up however, in the same ways they do stuff like machine learning (which also has good aspects and applications separate from the capitalist swill, but I'm digressing), because it appeals to several easy things. It's a tech solution that the average person knows almost nothing about beyond vague hype, it could hypothetically be used in ways to make the line go up harder, and the potential promise of it lends to fearmongering. If we don't do X or Y, maybe China will crack it. If we don't fund the tech billionaires, the enemy could crack super AI's etc. It's all the same bullshit.

Which is both ironic and unfortunate, aside from the obvious imperialist aspects, because stuff like Quantum Computing and Fusion are never going to reach the results people dream up without international cooperation. They are inherently big and hard problems, not the sort of thing one genius can solve. These big things that could fundamentally better humanity require humanity to work together to achieve them.