Of course you should buy altcoins as altcoins are the shortcut to make good profits in quick time which may never possible with bitcoin as to make profits from bitcoin you need to hold it for a very long term but in altcoins you can make regular profits if you have good knowledge of it.
Theoretically you are right, but things may not work like that in fact. few people can gain profits for a short term, especially when the market is going down, maybe you can win one or two times, but i think you will lose most profits finally