Some quick thoughts:
Cryptocurrencies' current valuations are largely based on speculation and trading rather than actual usefulness. It is simply difficult to belief that Bitcoin is actually worth thousands/BTC because of its rather slow transaction processing which is a problem inherent in the system which cannot be fixed. Ever. Not with Bitcoin.
In the alt-coin market, the sheer number of coins makes it very difficult to believe that any one coin can win out in terms of usage as a global decentralized currency. This is important when it comes to adding value to crypto because, with too many options, people can be driven away from using any coin at all.
Furthermore, most crypto models are extremely problematic in terms of their energy usage. Bitcoin is designed to increase electricity consumption in mining exponentially as time goes on, while most other cryptocurrencies also inevitably experience rising mining difficulty as they become more popular. One possible solution to this is Garrett Camp, a founder of Uber's, planned cryptocurrency Eco Coin which only lets miners contribute a minimum amount of computing power, thereby eliminating any "wars" of escalating computing power and energy usage. He is giving free coin to the first billion humans to sign up, which can be accessed at https://eco.com/.
In order to truly become a global phenomenon, crypto must adapt to the problems outlined above and many more, such as the lack of regulation which would make it impossible to accrue the political capital required to allow crypto to exist in the future as it does in the status quo. Because of the decentralized nature of crypto, it is therefore unrealistic that any coin that currently exists will actually go fully mainstream because they largely cannot adapt to problems after they are invented.
... but we are on the way!! Even "Nakamoto" with his published paper in 2008 discerned that it's still to optimize. It's in its infancy but hey, I think the political/economic trends fuel developers to keep working hard for progress. In the end just the tiny bit of sophisticated ones will gain acceptance and win though, but as you said, still a lot do...
Absolutely agree! I think the major issue with the current market is that some people think that Bitcoin or other alt-coins will actually become used regularly, which is pretty far from the truth and leads to some bad investment expectations (e.g. Bitcoin has gone up X% in 2017, buy yours today because it will also go up by X% in 2018)