In terms of tech innovations in the modern day, 15 years is an eternity. Google didn't take 15 years to become a massive search engine, FB didn't take 15 years to become the dominant social network.
Bitcoin was supposed to have started acting counter-cyclically (like gold) when it got mass adoption. So, 2018?
Instead, it acts like leveraged NASDAQ in its pricing, and has absolutely none of the utility that a cryptocurrency probably should have. The only benefit of bitcoin is name recognition. That doesn't create a currency or a store of value. The volatility of BTC/USD has only increased, as well as the correlation with QQQ, which does not suggest that BTC will ever become a store of value.
All fundamental signs point to a $0 value for bitcoin. Unfortunately, the dinosaur coin (BTC) will probably drag down the coins with utility (eg Solana, Zcash, and Monero) with it.
It is notable that Bitcoin took fewer years than both Google and FB to reach a 1 trillion market cap. Now market cap is a pretty horrible metric (and 1 trillion is arbitrary), but one way to compare totally different things. Note that bitcoin has always been the dominant cryptocurrency, and google/FB were dominant search engine/social networks much earlier than they reached 1 trillion market cap. What took a long time for them was for the market to value those innovations more highly. In crypto's case, the market valuation actually came quite quickly.
> The volatility of BTC/USD has only increased
Do you have a source for this? The data I have seen is that it is just slightly decreasing if anything, but there are many ways to measure volatility.