I just wrote an article touching on a lot of similar points. BTC needs to step back and allow the alt-coins to stand on their own if true diversification is to take place in the crypto world.
As you mention, one of the major factors to this is the current situation with Coinbase being one of the few fiat gateways and only offering a couple of direct purchasing options. We need to diversify fiat gateways and their offerings as quickly as possible for the market to be able to withstand a longterm Bitcoin recession.