Not sure why you're getting downvoted; I do think you're bringing up a valid point against my original comment: DH is susceptible to Shor's algorithm, too. That being said, the question is how long is it going to take to break a single DH key once we have adequate quantum computers? If it's in the order of, say, a couple months to a year, a ratchet algorithm will still protect privacy in the grand scheme of things, as it won't be feasible to decrypt more than a couple select messages per computer per year. Sure, quantum computers might improve, get cheaper and everything but on what timescale? It's not unlikely that that'll take many years and by that time no one might care about your private messages of today anymore and we might have established a new set of cryptographic schemes that are quantum-resistent.

Quantum computers don't exist. If you want to talk about a hypothetical machine which might exist in the future you should state that plainly.

Forcing the reader to parse thru the literary devices in order to get to the argument weakens the argument.