I don't think CNs are bad, as a method of income that doesn't directly increase your corruption root cost, it has some interesting benefits.
Even in SP, on VH its a nice way to dodge having to fight tough wars against the normal TC regions. Back in the days before gold depletion nerf you could keep your trade node somewhere stupid that you didn't get treasure fleets, develop CN gold mines for 170% the normal gold income (and he might go plutocratic while you would not, so you can add another ~10% to the relative calc) that you would get for developing your own gold mines, all inflation-free.
And before the tariff nerf you could easily reach a point where building manufactories in your CN was stronger play than building said manus in your home land (even ignoring potential benefit of longer trade steering chains). I think this was the point Groogy was attempting to make, unfortunate it was not as well-argued as it could have been.