Your mistake lies when you think that "when the price of bitcoin goes up, the price of the altcoin also goes up", that's where my thinking is wrong. because in crypto trading it cannot be guided by the movement of bitcoin because all altcoins have their own trends and movements. so my advice to invest in altcoins should not be guided by bitcoin but based on developmental information about altcoin itself.
I think he is right because altcoins will experience an increase in price if bitcoin continues to increase, look when bitcoin is experiencing a landslide, all the altcoins will experience it too. That's why all altcoins don't experience such an outrageous trend if bitcoin is doing well