This is a great point. We need to stop using these analogies. They make sense to explain how cryptocurrencies can be consider an investable asset like a commodity, such as gold, silver, oil. But that's where they analogy ends. These commodities have a practical use in market consumption activities - i.e., gold is used for jewelry and electronics, oil is used to generate power, etc. Cryptocurrencies provide much different purposes in the market place and we should just start talking about them in these terms.

Bitcoin's tangible function (beyond being an investible asset) is to be currency.

Ethereum's tangible function (beyond being an investible asset) is to be a coding language and structure to create blockchain tokens.

Lumen's tangible function (beyond being an investible asset) is to facilitate financial transactions among fiat-based banks and entities around the globe.

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To the OP's original question - do you think all cryptocurrencies will become "dead" in 40 years? Or is it just bitcoin that you believe will become obsolete?