Friend, I understand where your confusion comes from. Let me explain.
UniSwap does not exist in a vacuum. It is part of an ecosystem.
To understand how good it is, let me give you a specific example.
You’re a person in the United States and you want to buy some MAID from a DEX. You are ready to pay a 10% premium for not having KYC and you really have no choice where else to buy.
You buy MAID and the price in UniSwap goes up by 10% compared to ETH. At the same time, a trader on the centralized exchange Bittrex sees that the price has risen by 10% and he is making an arbitration. He sells MAID in UniSwap to get that 10% and buys in Bittrex more MAID. The difference is a profit for him.
At the same time, liquidity providers in UniSwap also benefit from fees.
You have a WIN for the person from the USA, a WIN for the trader and a WIN for the liquidity providers. I hope this helps 
