Additionally, the fees of the network can only be paid in ETH, which means that any use of the network implies ETH demand.
Whether people transacting on the network care strongly about the costs vs alternatives to create a proper link with fiat is not so easy to show because there isn't always a direct 1-to-1 correspondence between services (and there are switching costs, too) - so the "inherently priced in fiat" is tough to show, I think. Also, being priced in fiat might still not create demand for Ether from fiat holders - that comes from outside demand as per the above.
Demand to settle a transaction on the network is demand for ETH. Because the base_fee of a transaction is burnt, destroyed, so ETH needs to be acquired to use it as a settlement layer. Much in the same way to how heating your house with a gas boiler is demand for gas. Similarly, when natural gas prices skyrocket (cue Ukraine invasion), alternative forms of heating start to look more attractive, and consumers may change their behaviors lowering the thermostats. In the case of Ethereum, alternative settlement layers will look more attractive or some users may lower their use. The same mechanisms are in place. I agree though that the relationship is not linear, that's not what I implied. Simply that the revenues of the network are priced in fiat, because the price is set by an auction to include your transaction on the scarce blockspace. And given at least some users will be sensitive to the price of the transaction in USD they will, at the margin, set the prices for a transaction in USD and therefore the fee revenues of the network.
By the way I appreciate you engaging rationally on this topic in HN. Not a common sight when discussing anything related to crypto but much appreciated.
I agree that there can be some link based on the utility of the network and with less of a speculative frenzy it might actually be stronger now. Not dissimilar to (other?) commodities, which have some link to economic activity but are not directly producing the activity themselves (and they can also have speculative phases). And commodities also have conceptual issues around their use in long-term investment for that reason (but at the same time they exist and trade).
Nevertheless not all cryptocurrencies satisfy the above. The prime example being Ether. In the last year it has experienced -0.186% circulating supply inflation (i.e. it's non-dilutive to its holders) [1]. While the network has captured around USD 6.5M per day ~ 2400M per year in fees due to its usage as settlement layer which are paid to its stakers. Basically, it's cash-flow positive and does not rely on greater fools to sustain its economics.
[1] https://ultrasound.money/ [2] https://charts.coinmetrics.io/crypto-data/?config=JTdCJTIybm...