I completely agree.
Long-term, I don't think any of the current swath of cryptocoins has a compelling reason to have a high valuation. None of them are particularly useful for any practical (legal) purpose, although cryptocurrency bulls will deny this until they're blue in the face.
Current cryptocurrency valuations are primarily a product of rampant speculation, hoarding, and illegal activity. Bitcoin is the only cryptocurrency that ever achieved anything like wide acceptance as currency, but its insanely low transaction rate and high fees have made it no longer useful for that.
That said, it's hard to resist the gold rush. People who bought cryptocurrencies when they were cheap and are selling them now are making tons of money. The ROI, if you time it right, is absolutely insane. But the risk is also astronomical.
Last year I started treating cryptocurrency as a (very) high-risk speculative investment. I invested a small amount of money that I could afford to lose each week, spread between Bitcoin, Ethereum, and Litecoin. When the average value of my original investments had doubled (or more in the case of Litecoin), I sold enough to recoup my costs plus taxes and left the rest invested. I'll continue to do this as (and if) my small weekly investments continue to rise in value.
I fully expect the bottom to fall out eventually, but by investing only what I can stand to lose and by recovering my costs frequently, I hope to maximize my potential gain while minimizing risk. The tricky thing will be timing it right so that I can sell the majority of my holdings before the crash happens. But if I time it wrong, my overall losses will at least be minimal.
Disclaimer: I'm not even remotely a financial expert, I have very little investing experience, and I'm basically just doing this for fun. I strongly recommend not investing in cryptocurrency.