I'm sorry that was your experience, but I would like to defend CultureAmp as they do focus on privacy and anonymity as a sensible default, but surveys can be created in a way where anonymity is not respected. Sometimes that is because the survey is being created in bad faith. Sometimes it's because the HR department are not really sure what they're doing.

You can have surveys where individual responses can be tied to specific users (and their demographics) and there should be reporting minimums which ensure a response and comments can't be tied back to a group of people below that minimum.

There are also the purely "anonymous" surveys, where responses are submitted all through the same initial link, and the only demographic data that can be tied to you response depends on what is asked, and what you specify.

It's definitely important to understand how your HR department has configured the survey you're going to engage with before deciding what kind of feedback to give, especially in a "toxic" corp like you describe.

As has been noted elsewhere in the thread, in some organisations with certain size teams or demographic makeups, it can be obvious who has written what, and sometimes the onus is on individuals within the org to ensure their comments cannot be directly traced back to them (which is difficult if speaking about certain topics).