The dot com vision was e-commerce, but the killer apps came in the form of social and search. In crypto, its still to be seen where the killer apps are.
I don´t think this killer apps will be about cryptocurrencies. Why? Because you need a real crypto economy generating value for many people.
A crypto-economy is not people buying and selling Bitcoins, but people earning Bitcoins in exchange for their work, products, and services. Then -and only then- some cryptocurrency will emerge to become a global standard.
The economy is first, then money emerges out of the economy. Not the other way around (important reminder for the Bitcoin maximalists).
NFTs are emerging as part of a real, native crypto-economy, creating digital assets out of property, utility, intelectual property, etc.
=> Are NFTs going to become the missing killer app in crypto?.