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Look, it depends on what your priorities are:

1) If it is about short term investments and you don't mind taking risks to maximize returns over what traditional investments like stocks give you and if it is as part of a balanced portfolio then YES.  Ideally, don't invest cash in crypto - do mining
2) If it is about long term investment and retirement plans, then absolutely not

Why?  because no one is yet clear if crypto currency will pass the test of time.  According to some very influential people e.g. JP Morgan CEO and others, it is a bubble.

Historically, traditional currencies were backed by Gold to guarantee value and that value could be exchanged for goods and services.  Today, they are backed by Governments/National Banks and can be used to purchase goods and services.   So essentially it is "backing" and "exchange/usage" that decides the value of any currency.  Crypto doesn't have that (no backing by institutions or governments in overwhelming majority of the cases to guarantee the value) and in majority of the cases, you really can't use crypto currency to make purchases or exchange it into something which would give it a "usage value".   That is why, the market for crypto is driven entirely by other factors which cannot be quantified and hence is very volatile.   

The government backed cryptos are years away and in most cases are being done to hedge risks on national currencies.  But even in this case, you end up having useless cryptos e.g. Venezuela because at the end of the day, these will be linked to tangible stuff like economy, assets etc and not in the air like a theoretical limited supply aka Bitcoin which doesn't have backing or usage value.  And in the event these materialize in 10-15 years, it would mean that the current non-government backed currencies like Bitcoin and others, will disappear. 

To summarize:

1) Investors  cannot assign appropriate value to the currency as you can with traditional investments
2) You are buying the wrong asset.  Block chain has value but digital tokens linked to it have none i.e. you don't get to have ownership in block chain by buying crypto.  And block chain is far from becoming relevant at this point in time
3) Trading is decentralized and it is by retail investors.  Which is why you have such a high volatility due to emotions playing a large part.  In the case of stock market, despite drops and falls, the volatility is not that much due to institutional investors holding their positions and being data & not emotion driven
4) It is not regulated and there is very little understanding on part of most of the public on how this works.  As Warren Buffet says, never invest in a business you have no understanding of

All of this can change in the future but at the moment, it is a game of HIGH RISK HIGH REWARD.  If you want to take that risk, then by all means.  In the long term, it can go either way i.e. adaptability or shut down - if you got into crypto early and got your position at a very low cost, it is ok to hold but if you are doing it now i.e. within last 3 years, then I wouldn't advise it as you are buying at a price point which, if things go the wrong way, can wipe you out.