Yes, it will be wrong to go ahead solely with Bitcoin when we have hundreds of cryptocurrencies. I personally invested in 36 cryptocurrencies at present of which 5-6 have more funds than what I am holding in BTC. Along with this, I also invested in Mutual Funds and Stock Market.
Everyone should have similar strategy to make maximum profits.
Focusing only on Bitcoin be a fools act, but till now only few altcoins seems to be promising.
And Newbies basically sticks with Bitcoin because they entered crypto world with BTC and the trust is strong and also it had showed its potential.
But once they understand this, indulging in others, will actually help to increase wealth much faster. Bitcoin reached a point where it will increase for sure, but it might take time to rise gradually.