They're not though.
GC mentioned "total factor productivity", which is not just an assumption that things will stay the same. It's a measure that value (productivity) actually is increasing, all the time.
And the other rebuttals were pointing out flaws with GGC's arguments, none of which relied on "the status quo works".
Not surprising though, pretty much everyone born in the past 60 years has become accustomed to a ridiculous "normal" that has been built on a fossil fuel house of cards.
https://en.wikipedia.org/wiki/Normalcy_bias