I think it's overly dismissive.

You can have valves that are pretty close to end of life that will work in circuit but they are very far from optimal.

Valve testers are also really good for matching valves. Without them you have to listen for channel imbalance to see if you have an issue. Not good.

So I take that article with a pinch of salt. Though some points are no doubt valid.

I am no expert but I have a tester for testing a large triode collection and so far it has proved really useful and certainly appears to tell the truth.