I think they can
You're wrong. Bitcoin is the father of all the coins here and altcoins are just clones from bitcoin, having its name Altcoins that means
Alternative coins, they are clones and forks according to the article that I've read in quora, in Math, bitcoin is the original equation and Altcoins are just the derived equations from it, without bitcoin, blockchain and all of other cryptocurrencies would not exist.
so it is accurate to assume that altcoins could never replaced bitcoin, ever, but I've seen many that tried so far to do this *sighs*