Maybe, but centralized services seem to have that problem too in practice.

Yup. Instead of having multiple echo chambers on one centralized network, let's now have multiple echo chambers on a decentralized service where it's even harder to hear opposing viewpoints!

The sad reality is that humanity is not ready for something like the Internet. If you said dumb shit in your town's square, you'd get hit upside your head. Say it on the Internet, your little numbers go up and you get a dopamine hit.