I disagree with this statement.
The whole purpose of ethereum is NOT to creat ICOs.

The real purpose is to be able to create small programs (smart contracts) which can be executed without a central authority.
Just because the majority of people are using them to simply create ICOs where they just build some kind of a payment token and promise a lot of utility, this doesn't describe the usage/purpose of ethereum itself.
Most people are greedy. Thats the reason we have so much shitcoins and tokens now. They all just want to make fast money.
But this does no way mean that the whole ethereum network has been made for this one purpose.


@OP
I think it heavily depends on the reason for BTC going down.
If it would be because of a security vulnerability, the chances of ALL cryptos going down would be very high, IMO.