a perfect and quick to setup quantum computer can crack quite a few types of encryption quickly
Not really - at least not the "quite a few types" bit. Basically it's RSA, DH, and DHE; and anything with a key that's too short. Those are commonly-used algorithms (well, maybe not the last, these days), but it's a short list.
IIRC there are though some types that take a similar time to unravel as on standard turing machines.
Entire families of algorithms, in fact. Lattice, multivariate, code-based, and supersingular-isogeny are the main ones.
So changing algorithm is possible (but currently not worth the overhead as there is no risk or need).
Actually, it's already underway. NIST and other standards bodies are running competitions for viable "post-quantum" algorithms. ("Viable" means they offer reasonable performance and key sizes, and have been sufficiently analyzed without their security claims being unduly undermined.) Google and others have created test TLS suites using some PQ algorithms and done some testing with them in the field. In fact, it looks like Google and Cloudflare are conducting experiments with PQ suites in TLS (specifically CECPQ2 and CECPQ2b Kx) now.
We will almost certainly have PQ crypto in widespread use (courtesy of public HTTPS with major volume players like Google participating) long before there are any large general quantum computers known to the public. My belief is that it will happen long before there are any large GQCs, public or secret, in existence. I won't be at all surprised if there are no large GQCs in my lifetime.