Congress could easily delegate additional discretion to the IRS, they just haven't yet as they have been unprepared for this outcome.
When you look at the universe of assets, they either exist in walled gardens (brokerage accounts that there is no expectation to withdraw from, or that you simply can't withdraw from), are not easily divisible or have separate denominations if they were, or are impractical to transport (a barrel of oil, other spot commodities), or are not fungible (art, collectibles, barter assets).
All crypto assets transcend and overlap with the fungibility of every other asset class all at once, while being able to function as non-fungible assets if desired.
Congress has considered this matter already, and they have chosen not to treat cryptocurrency as a domestic currency by refusing to consider bills that would classify cryptocurrency as a domestic currency.
Non-domestic currency (i.e., foreign currency) is treated as an asset under US tax law, and as a currency not issued by the US government, cryptocurrency is a non-domestic currency and is thus subject to the same tax treatment.
All of that other stuff you said is irrelevant.