It would require a hard fork, but it is technically possible to increase the divisibility of the base satoshi unit. And it should be an uncontroversial change if needed, since it will not require any redistribution of money.
With that said, it doesn't seem likely that the value of a bitcoin will increase in the near future to the point where we will actually need more than 21 quadrillion units of precision.
From my limited level of understanding, it seems that the only differences are that you know that Bitcoin has no inherent value at all (gold has some since it can be used to make jewelery and gold-plated audio connectors, among other things) and you know exactly how much Bitcoin can ever be mined.
Instead of explaining what Bitcoin actually is you compare it to something very simple that everybody knows and derive "digital gold" ...
[1] https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...
[2] https://www.metalary.com/tantalum-price/ [3] https://www.bullionbypost.co.uk/gold-price/today/kilograms/u...
I've moved to altcoins for sending money, the transaction fees of bitcoin finally pushed me to another one.
I wish I'd buy a little extra to speculate myself, but I'm pretty impatient so I'd better not.
Also, please take your "digital gold" meme and use it on r/Bitcoin. Not only does Bitcoin's price contain the speculative valuation of a million people who call it a currency (regardless of your particular vision) but that vision also has a million flaws. It's rather funny, when someone points out its flaws as "digital gold" then the Bitcoin troglodites come out and call it a currency. When you point out its flaws as a currency, they correct you that it is, in fact, digital gold. When in fact, it's just a technology medium for transmitting value without the economic mechanisms to be a currency, nor the historical/economic/political/social mechanisms to be a 'digital gold'.