Bitcoin is still the base of all alts . To buy alts you need to buy bitcoin first
No you don't.
Bitfinex isn't a small exchange, all pairs exist in ETH now. Bittrex & Kraken have many ETH pairs.
Also I would be worried if the value of BTC was significantly based on that fact that it's bought to buy ALTs.
So far, when ALTs were going down, money was going back to BTC. Quite a problem if it goes to ETH instead.
because bitcoin has implanted its roots on the economy and that roots are too far down to be uprooted easily.
Where were you when the BCH flippening was happening? The first one was really scary, there was a direct pipe between BTC & BCH, and if a megadump hadn't happened (thanks for that) when the BCH had reached 0.5 BTC... that crap may be at the top right now.
So keep that in mind, people are there mainly for money, they aren't loyal in any way.
Top second crypto is a generic one that looks like a good challenger. Top third isn't even decentralized. Top fourth is a scam. There isn't any logic at the top, it's all speculation.