Please make the effort to understand the difference between frontend and backend.

The nice thing about the decentralised exchanges such as Uniswap or -dydx- is that you do not need their websites/ frontends because their smart contracts/ backend is available on the blockchain. Anybody can make a website that interacts with any smart contracts on the blockchain. There are even aggregator websites (e.g. https://app.defisaver.com/).

Do you know any website that aggregates the services of any TradFi banks and brokers?

Edit: Actually dydx is layer 2 now: https://dydx.exchange/blog/layer-1-wind-down