>>How do you foresee cryptocurrency alleviating those problems when existing capital can simply produce and acquire the majority of coins/tokens in existence?
That is still a net gain for society.
Look at it this way: cryptocurrency could potentially replace high rent-extracting institutions, and it would only be able to do so if it provided its owners with much lower levels of economic rent than the institutions it replaced (that's where it derives its efficiency advantage). Just to clarify: economic rent is defined as income that is not derived from productive activity. It is unearned, from a broader economic perspective.
So now imagine the wealthy shareholders of Goldman Sachs sell their shares, and buy up all of the cryptocurrency. They're still very wealthy, but the assets they own don't hold the same unfair advantage that the GS shares that they once owned held.
That is what it means to be in a fairer world. Eliminating opportunities for exploitation (which can roughly be mapped to rent seeking) is how you durably reduce income unequality.
>>That's oddly simplistic. No mention of wages, education, and tax policy?
It's simplistic because it's a very broad analysis that only distinguishes rent-seeking from none-rent-seeking activity.
In this case I think it's appropriate given cryptocurrency has the potential to have a very fundamental impact on the macroeconomic picture. Moreover, speculating about the finer details of its impact might not be all that useful, given how hard it is to anticipate exactly what those more specific effects will be. The broader effects are easier to predict and thus a more appropriate object of speculation in my opinion.