Almost all altcoins rely on bitcoin when it comes to the price so I think its very important that bitcoin should always be on the game. As we can see whenever bitcoin goes up or down the altcoins gets affected so it means that without bitcoin altcoins wont survive because people will think that crypto will end if bitcoin wont be that valauble tonpeople anymore.
you are right and maybe if bitcoin does not exist, there will be other coins that will replace bitcoin as the leader but this is too difficult because that coins need to have a function like bitcoin because that coins will be like an adjusting for the other coins. and the bad scenarios, if bitcoin does not exist, is the cryptocurrency will disappear and I think it will replace with other technologies because I am sure that the new technologies will come out among us.
Generally, there is no direct relationship in between bitcoin and the altcoins because the nature of both crypto coins is entirely different and that there is nothing common in between both the coins. Even then, if there comes a situation when there will be no bitcoin in this world, then this will create a lot of difficulties for the ones who are investing in different altcoins as the market will fall significantly.