Nothing is tied to BTC, if BTC drops the rest will eat market dominance, and go upp like any commodities on any market, if the market does not move.

If the whole market goes down, everything goes down, unless they outperform the market.

If the whole market goes up, BTC can still lose dominance and fall against ALL other cryptos, which has happened... In feb 2017, bitcoin moved sideways and lost 50% of its market, guess how? Other cryptos went up and took the market shares! Do not make it more complicated then it is.

Anyway, remove BTC and nothing changes, we can still buy and sell eth/neo/usdt/bnb etc via other pairs, and the other pairs wont be affected in its value due to this.

ETH is equally worth 400 dollar with our without going via BTC, which no one does any longer.

There are many on excahnge coins as well, moving just fine IT is called gaining market shares, outperforming the market, taking market shares by having a better product.
This is standard market movements and nothing special, BTC is of no relevance!

Peace