The thing China can do, and does do: Kill your network connections, whether that's a TCP session, your ability to send or receive packets with some particular IP addresses, or at the extreme armed men show up and now it's not an Internet problem.
Things China can't do: Magically "downgrade", "decrypt" or "intercept" the secure protocols we use every day like HTTPS. Facts won't budge, the technology we are using does what it says on the tin.
The Internet can't route around you being thrown off a tall building by men with guns, but the IETF has for some years considered it to be extremely important to design the network protocols to prevent these shenanigans. BCP # 188 "Pervasive Monitoring is An Attack"
My guess is if you are in China they can MITM you with their own root certs.
> Things China can't do: Magically "downgrade", "decrypt" or "intercept" the secure protocols we use every day like HTTPS
I mean... They could, though, no? If they control the gateways they could drop any traffic that isn't encrypted with some root cert that allows them to decrypt in transit packets.
Yes China will kill your network connections. And that is proof that Internet cannot route around censorship. Any time Internet routes around censorship China finds a new way to censor it.
Normal people don’t care about “downgrade” or “decrypt” or “intercept” they care about availability.