They can’t force ISPs to block all of the VPN protocols in general
They very much can, I've seen it happen last year. The main protocols are VERY easily recognizable by DPI. However, there are obfuscation methods that can get through even Chinese Firewall, and they're constantly improving.
Most of the mainstream social media is blocked where I am. Good news: a huge part of even uneducated population does indeed learn to evade censorship. Bad news: they tend use the most easily-accessible services, which are sketchy, like reselling the users' IPs as residential proxies.