I partially disagree with this argument. Since Bitcoin preserve backward compatibility, that means people need to move their coin to address which use better cryptography. There's also consideration new technology (such as SegWit and Taproot) took many years before it's activated on Bitcoin network. Although for now, there are definitely other higher priority than choose and implement QC-resistant cryptography.
You are right, should we be faced with the possibility of this happen where a quantum computer is created to break the hash then, there is definitely going to be a transfer of addresses to a better and more secure cryptography. Nobody is actually ruling out this possibility but the only thing is it wouldn’t come so sudden and at such there will be more time for a switch away from the current algorithm.
Satoshi himself is looking at that possibility as he clearly stated here
SHA-256 is very strong. It's not like the incremental step from MD5 to SHA1. It can last several decades unless there's some massive breakthrough attack.
If SHA-256 became completely broken, I think we could come to some agreement about what the honest block chain was before the trouble started, lock that in and continue from there with a new hash function.
If the hash breakdown came gradually, we could transition to a new hash in an orderly way. The software would be programmed to start using a new hash after a certain block number. Everyone would have to upgrade by that time. The software could save the new hash of all the old blocks to make sure a different block with the same old hash can't be used.