It has _everything_ to do with usefulness. If it is useful, it should be
either fixed or left alone. It may just work for people who use it.
Sometimes it does take years to fix something. Some fixes are way more
involved than you think. All you can do with it then is staying aside and
watching, if you don't want to participate in heavy lifting or massive
code churn. That's why the pragmatic thing is to leave those packages alone,
if you personally cannot do anything.
One of recent examples is the story of fixing Octave. Your approach
would be to kill the package even if it just worked for some people due
to some unknown magic. OctaveForge package is another heavy lifting
which should be done nevertheless, if you want wider pkgsrc acceptance.
Your approach here is to remove it and thus reduce the value of NetBSD as
educational platform. I understand that you may care nothing of educational
packages, but then you shouldn't cramp others' efforts.