Uniswap the company is entirely disconnected from the uniswap router which is what defi really is. The uniswap router is what completes transactions on the blockchain. Not the uniswap website. The uniswap website simply provides a front end for interacting with the uniswap protocol.
You can easily, like less than 100 lines of code, write your own implementation of the uniswap swap functionality. This is why it truly is decentralized. Uniswap the company has no way of preventing you from doing that in their v1, v2, or v3 router.
Further they themselves are not running the router. Anyone who is running an eth node, or miner is running the router. So yes, uniswap has a financial interest in making a commercially successful product. But that product is uniswap.org/app
It is not the smart contract. The smart contract is what makes it decentralized.
Their only argument besides the financial interests of the companies who created the first defi products is claiming that blockchain rewards lead to concentration. Which is the same argument that has been made since bitcoin was first launched, but every single day the likelyhood of any sort of attack related to concentration becomes less likely. As more people start their own mining operations and start hosting their own node.
If someone wanted to centralize the chain they missed their opportunity. Because it is simply not feasible for it to occur at this point.
Like usual, old school economists desire to control crypto markets. But they know they aren't able to and won't ever be able to so they write ill informed articles filled with factually incorrect claims in order to misled policy makers to implement laws to attempt to regulate the industry. Which will also fail.