It is not as much of a risk as some westerners think. Unless you are actually activists planning change, it is unlikely for CCP to disappear everyone that speaks against it; especially on non-Chinese platforms. On Chinese social media, on the other hand, dissents will be de-platformed quite quickly; I think some might receive couple warnings and/or threats before they are in physical danger.
However, it is not uncommon to hear about larger platforms being threatened by CCP with their own safetys or their families.
In the end, for many people, it is a large enough risk with barely any reward. Everyone knows CCP is oppressive: maybe not every western media report about China was fully truthful; but with these many reports, some have to be true. On the other hand, tankies aren’t going to change their mind because one anonymous “Chinese” on the internet speaks up against CCP. Speaking up against CCP really will not bring that much change, especially given the potential of putting themselves and their family at risk.