Actually Bitcoin price often influence altcoin price but there's a season where altcoin do extremely well even when Bitcoin is stagnant or declining. What if this season comes More often, what will be the faith of Bitcoin?
There are times where bitcoin just stagnating and BTC dominance decreased which in other hand also means that people are rotating their money to altcoin, if the dominance dumped so fast, it means an altcoin season so yes altcoin can do well even if bitcoin is stagnating.
Although altcoin pricews strongly tied to bitcoin, price action wise and if we see the chart at higher time frame that isn't always the case.
The problem is right now the dominance just keep increasing and showing no signs of weakness so as a result altcoin got wrecked so hard.