if you actually check the charts you can see that altcoins are actually getting dumped these days but when you look at their USD value it seems like they are rising.
what happens is that when bitcoin price rises, everyone pulls out of the altcoins so they get dumped against bitcoin but for example if bitcoin goes up 10% they get dumped 9% and that 1% difference looks like USD value rise and you think they are "gaining" whereas in reality they have been dumping.
Let's check the charts.
ETHUSD is up 78% this year. BTCUSD is up 42%. As one would expect, ETH is rising against BTC:
We can see the same thing on DASHBTC and many other altcoins. They have been rising against
both BTC and USD. In other words, they are outperforming BTC, at least so far in 2020.