It's definitely possible that people complaining about phony apologies are doing a power thing... Hmm, maybe they want to take away power from people who do bad things?

It would be nice if there was some kind of way to signal true remorse, like a way of speaking with our bodies, a "body language".

No one says the behavior doesn't matter - but without an expectation of social cost (apologies, and further criticism and reputation loss when the apology is tone deaf and insincere), why would anyone care about behaving well? Demanding apologies isn't worthless - it's a power thing.