You said it right. I think it is the same story with Ethereum...so many people considered it to be done when last year it experienced so many challenges and problems but look what happened now the value is rising and it is now considered to be the number two. As to Zcash, if there is really a good community of people behind this one, then we can expect it to soon rise again in value. I know it has a history of being overvalued but this day it is now setting to where it should be. Zcash remains to be in the top 10 and that is already a feat in the first place.
That is mostly true. But I believe, that most altcoins out there like Ethereum are just hype. Being an inflationary cryptocurrency, it is not meant to be a store of value, in which I believe that it is a little overvalued these days.
Considering that ETH, has violated the principles of immutability (which it is a key feature of the blockchain) and has shifted its view towards banks and big corporations, it may turn out to become centralized at some point in the future.
As for ZEC, it is also hype, as the only great feature it has is its anonymity technology, but lacks a GUI wallet and its inability to become used in other platforms like Windows and Mac. This certainly limits its ability to become mainstream, as people would want something easy to use without any prior technical knowledge involved.
But in the bright side, both ZEC and ETH have dedicated development teams (which most alts lack of), that will help them become more secure and deliver innovations as time goes by. If all goes well, then I expect for both cryptocurrencies to become mainstream. Just my thoughts.

The inflation of the Ethereum will be reduced in the future. A small inflation is actually good for the economy.