Diversification is a must in any investment really, you shouldn't put all your eggs in one basket.
This doesn't mean that you should spend your money everywhere without doing any research though. The projects must be rock solid with a good roadmap and a strong team otherwise It's not different then investing everything you have in one alt.
In crypto business better not invest only one coin. Diversification is a good strategy their must always a back up plan in case the other coin your invested in is crashing down. If there's a bright future for other coins or even other business divert to that opportunity.