The phrase buy the dip is only a good advice when you apply it properly by buying the very good altcoins whose value is only down because of the bearish market condition. Because it is not all coins that dip that would recover their value.
Looks like you are talking about Shitcoins and not literally altcoins mate, because a good altcoin will fall in bearish market but will surely recover and make movement up when the bull comes.
meaning if you invest make sure that the coin is legit and has a good roadmap and not just another shit projects that targets to be Pump and dump coin.
For example, early this year (when the market was super bullish) almost all the projects released saw good increase in their value. but that doesn't mean it is all of them that were very good projects. After the market dip (correction), most of them never recovered their value. The crypto market is filled with a lot of scrap altcoins and the market way of sheding them off is to dip (correction). So it would be in your best interest to only buy very good coins in the market dip.
There are so many scammers that riding the growing market , they even join each Platform that performs best fooling investors that they are really connected unto that , but after gaining investors money ? they will gone .