completely wrong , Diversification does not have to be occasionally but each time mate , we must have many coin that single investment and this has been proven for how many years now? though determining the coins to keep hold is the harder part but diversifying is what investors in our time now must have and trust me you will also love having those in daily basis.
There are investors that have been lucky with some other altcoins and that's why they're pursuing altcoins. But there are also people that have been successful with lesser investments in altcoins and are more focused on bitcoin thus, advocate to invest in bitcoin.
the riskiest investment in crypto are those altcoin investing , if we are not ready to lose and not really that deep in knowledge ? better try to listen to your instinct and help your money be safer , But bitcoin in majority.
That's true, choosing the altcoins to invest in is hard because you'll never know if the one you've picked is going to be good in the future. And that's the reason why we have to research first before buying it.
diversify that is the key , risk for altcoin even shitcoin but keep bitcoin in major investing .