These days it seems like altcoins are doing better than bitcoin because pretty much all of their prices are green while bitcoin price is red. its because bitcoin act as aa bridge to buy and sell altcoins, that contributes a big factor.
Yes, because bitcoin is the basis of the price of all cryptocurrencies and also bitcoin have the highest price, but bitcoin is only one and a lot of altcurrencies are all in the market. Bitcoin still take control of the market.