Does the concentration of investment in certain coins threaten the crypto economy?

I know this has been brought up in various discussions, but I couldn't find any threads dedicated to a discussion of this. Right now, there are only a few major coins (Bitcoin and Ethereum being the largest) that have far greater total value than most, other coins combined.
I don't know the answer to this, but even though in theory, one of the great things about cryptocurrencies is that if you can find a way to take an aspect and do it better, you can create your own coin and it will be adopted by people who value that, in practice that doesn't seem to be happening as much anymore. New coins have to constantly struggle against the established titans, and even though there are events that push people to smaller coins (ETH's gas price spike for example), for the most part, most of the money seems to stay with the major coins. Sorry if this is not well phrased, but it's just something that's been bouncing around in my head for a bit.