Technically correct, but some of the problems we want quantum computers to solve are currently infeasible by conventional means because of speed. Factorization for example, that's why public key encryption works (we can't brute force it), but a quantum computer could.

>> [..] but it is a lot more efficient for some of them.

> Technically correct

Not quite. We know algorithms which have better time complexity on a quantum than any known classical algorithm that solves the same problem. Shor's algorithm is an example. We are not sure if a classical algorithm with the same time complexity exists.

>Factorization for example, that's why public key encryption works (we can't brute force it), but a quantum computer could.

Most (all?) modern public key algorithms are not based on the integer factorization problem.

> Most (all?) modern public key algorithms are not based on the integer factorization problem.

There are analogues for Shor's algorithm for the discrete logarithm and other similar problems.

But most modern asymmetric algorithms are based on elliptic curves and other problems that quantum computers don't help with.