There has been significant hype around Quantum Computing over the past few years. While there certainly are a lot of interesting ideas in the space, especially in terms of mathematics, enormous engineering hurdles that are not clearly solvable stand in the way of practical quantum computers.
While much skepticism has been pointed in the past at efforts to overcome decoherence and error in quantum computers, I’d like to point my critique elsewhere. Even if we assume that quantum computers can overcome every engineering challenge that currently exists (which in my opinion is still an enormous if), even perfect quantum computers have a variety of other serious limitations that are only rarely discussed.
In short, while quantum computers may be theoretically exponentially faster than classical computers in some cases, there are also many other cases where they are exponentially slower, and even some notable examples of trivial problems for classical computers that arguably are not possible for quantum computers to solve at all.
Luckily, most of these do not actually require much understanding of quantum properties, only the reversible nature of quantum systems and some properties of wave function collapse.