As the market matures, this won't always be the case. This will gradually change once people get more familiar with Bitcoin. Currently it's the main vehicle for on boarding new crypto investors. As they become more comfortable with crypto in general, they'll invest elsewhere minimizing the effect.
The main catalyst for removing Bitcoin dependance is when exchanges that support many alt coins have direct fiat pairs. Right now, due to the challenges in getting money service business licenses in multiple jurisdictions, most either use BTC/ETH or USDT so BTC is typically always involved somewhere in the process.