I do understand his point. If you want content to be long-lived, requiring the execution of code to render it introduces a risk that it will become much more difficult to correctly render in future, if it's not maintained and updated.
I think it's a valid point to raise, but how much you care about it is going to depend hugely on what you're doing.
Why would most js heavy companies want content to be long lived? What's the benefit to them? If they're concerned about making data accessible then they'll open an API that they hold the keys to.
The point is that js has become a de facto way of rendering content, regardless of its nature, and in some cases this impacts usability and other non-functional requirements in ways that people don't always consider.
Obviously if a company wants tight control over their content then this may work to their benefit - although they may still find that their ability to render their own content requires non-trivial maintenance over time.
But that's a pretty narrow view of the web, and not everyone publishing on the web fits that model.
I think it's a valid point to raise, but how much you care about it is going to depend hugely on what you're doing.