Bitcoin prices have a huge effect on altcoin. the effect is quite large. the decline of bitcoin can make the altcoin very drop in price. even though at that time they actually had no problems with the project but because the effects of bitcoin made a price drop
But I think it have no impact on all altcoins, you can see it in Binance there are some coins whose prices can go up to 40% even though the price of bitcoin just touched $3250 USD. Now it's very difficult to analyze the market because there are too many manipulations and panic traders.