First of all Marginalism doesn't explain anything.
Marginalism posits that the cost to produce an item is roughly what you can sell it for, barring a monopoly. It separates the labor from the price which explains why a bitcoin could cost both $0 and $5k to produce. Distorting the issue, however, is that bitcoin (crypto in general) is unique in that it is akin to a decentralized monopoly.
The code is the monopolistic owner of a resource and the code delegates how that resource is produced. Because bitcoin is decentralized, the code must introduce inefficiency (difficulty) to combat the duplication of infrastructure (mining rigs) from pulverizing the price to zero. It is therefore apt to say that bitcoin is "paying people to dig holes and then fill them up" because any miners beyond the first one are completely unnecessary
in the economic sense. Ideally, if we could somehow ensure that a single miner would function identically to a decentralized group of miners to the consumer, the single miner is the
far superior scenario as the duplicate and wasteful infrastructure is avoided and total profit realized is far greater. (Although this may be undesirable if you are a communist.)
Ironically, arguing for the usefulness of mining (economically) is in a way arguing a Keynesian idea (digging holes).
The utility of bitcoin is the same as always but its price is not, the cost is changing due to the changes in social situation so the value has changed and price follows the value. The "loosely" adverb you used is true for all commodities and is aligned wit Marx's theory.
The utility of bitcoin is clearly not the same as always. In 2009 I could not buy alpaca socks; in 2011 I could. Therefore in 2011 the utility of bitcoin was higher than in 2009. I think here you are trying to avoid any association with marginal utility so as to make your case, but utility is not the same as marginal utility. If you deny the utility of bitcoin has changed over time, then there is no hope of a productive discussion.
It also appears to me that you are conflating supply and demand with "changes in social situation", if not please clarify because I don't understand this argument. Perhaps you mean subjectivity, but that would be arguing against LTV. As far as the value changing because of it - this can't be correct under LTV because the labor
is the value.
Again it is somewhat difficult to peg Bitcoin in here because it is designed solely as a currency and thus has no value in use, and it is a decentralized monopoly which distorts many of the inputs and outputs of the situation. If you are going to make a strong case that bitcoin satisfies LTV, your arguments need work, imo.
Fiat money is not an ordinary commodity it started pegged to gold and diverged gradually to become what it is now: a scam. PoS issued currencies are the same as fiat currencies in this respect.
A false equivalence. No argument has been presented.