Gutmann is critiquing the fact that quantum computers don’t exist.

No, he is critiquing the fact that, despite a CRQC (cryptographically relevant quantum computer, eg, one large enough to attack currently-deployed cryptographic key sizes) having not been publicly claimed and probably not existing yet, people are spending a lot of effort designing and deploying new post-quantum cryptographic primitives based on the assumption that one probably will exist eventually and possibly soon.

If you think quantum computers don’t exist at all, what do you think the numerous customers of the companies listed here (who have been selling them for a while now) have been buying?

There is a relatively broad scientific consensus that a CRQC is likely to be achieved eventually. The belief that it must be impossible because it hasn’t been demonstrated yet is the baseless position.

Also, I suspect you’re not understanding the difference between quantum cryptography and post-quantum cryptography; they really have nothing to do with each other at all. Your post titles still say “quantum cryptography” which is a thing that Gutmann’s essay is not referring to in the slightest (and is a thing which doesn’t involve large quantum computers).