They're not saying it directly, but that's what they mean.

They are saying "X is not worth this huge valuation" which implies the person saying that thinks there is something "unfair" about the multi-billion dollar valuation.

But, this naysayer person has a proper "fair" valuation in mind based on their complete outsider knowledge. To them, it's actually worth nothing (no revenue == if someone buys it, they can't make money == it's worth nothing), but they'll concede a little since a lot of people use it.