You can use this argument against anything not done yet: "we've been trying to build fusion reactors for 50 years now, we should give up now"
We have fusion power on small scale, we don't have it on commercial scale.
Seems to be the same argument.
We have never had fusion power on a small scale (we have had fusion ignition/reaction, but never [afaik] generated usable power), let alone showed continuous growth in scale of that power over the years.
They're not the same. Fusion is a 'science' problem, quantum is (mostly) an 'engineering' problem.