And apparently, there is some confusion within the community about price increases in CoinMarketCap and people think that everything is going up right now, which is not the case. The green numbers you're seeing in the price page don't represent much. If you click on the coin though, you'll see the price in Satoshi... that's the one that should be increasing.
I'm afraid this doesn't hold true anymore. Years ago, the only main currency pair to trade altcoins was BTC. There was a Litecoin pair but it didn't pan out. Anyway, back then altcoins were exclusively priced in BTC hence holding alts was a great way to multiply your BTC.
But now Tether and other stablecoins are liquid enough that almost all altcoins are now priced in USD.