Quantum computers are not going to replace the computers as we know them. They can be considered like a GPU that will be attached to a normal computer, providing speed for some limited operations. Their usage will be very limited specially at the beginning and their price very high.
I agree that quantum computing doesn't offer an advantage in every situation. I think there is often a perception that quantum computers are just
faster than conventional computers, but that's not really the case. Where they excel is in dealing with extremely complex problems. The advantage of a quantum computer is that the complexity scales differently.
A conventional computer can solve a problem 'x' in 'y' seconds, taking 'z' number of steps.
If you build a faster conventional computer, it can maybe solve problem 'x' in 'y/2' seconds, so twice as fast - but it will still take 'z' number of computational steps to do so.
The advantage of a quantum computer is that it can drastically reduce 'z', the number of steps required. This is why they are 'faster'.
It's quite fascinating when you get into it. If you are interested, have a look at
Grover's algorithm.