I mostly agree with you but i believe that the truth is somewhere in the middle.

Of course it's not possible to have every coin paired with fiat, exchanges can't handle it.
However, they should have more fiat pairs with top coins. Also, there should be more pairs with other major coins like LTC, XRP etc, just like there are many pairs with ETH.

Regarding manipulation, i believe that the market is heavily manipulated. We can just check the charts for BTC, LTC, XRP etc and see they're almost identical. Obvious bot trading.

Whales today are not just early adopters who HODL, there are lots of funds that have bought billions of crypto and now move prices as they will to maximize profit. We can't prove it, but the facts agree with this theory.

Crypto is a young small and unregulated market compared with FX etc, so its very easy for them to do what they want. We small fishes just have to play along.