we cannot say this is the reason plainly to dump the the altcoins in this situation because Bitcoin is developing right now and moreover people like to invest in it the demand only decides the price I think that's why it is not going good well.
it all depends on the altcoin that you hold if you think they have good potential for growth, then you should keep holding the altcoin and if you want to invest in bitcoin, use other capital.
but if it turns out that the altcoin you hold does not have any potential even when the altcoin pump and the coin do not experience significant movement, it is better to throw the altcoin to switch to bitcoin or maybe to other altcoins which have better growth potential.