Thankfully, it’s not that simple.

A centralised service is an easy target for a government. (This is where Signal stands.) A decentralised one is significantly harder, because the government would have to be constantly discovering and processing every node in the network as new ones appear. (This is where Matrix stands.) Fully peer-to-peer decentralisation makes it harder still, because there are as many nodes as there are users and their network addresses might change all the time. (Some of these exist today, but are mostly experimental with few users. Matrix has done some proof-of-concept work in this area as well.)

On top of decentralisation, tunnels like VPN and Tor can be helpful in avoiding ISP-imposed blocks.