Assuming you are in the US, there is a safe harbour called "opinion based on disclosed facts" for that. You could also fairly argue that the conduct of a lawyer is a matter of public concern

> It really sucks one cannot publish something like "this guy charged me $5k, wrote my name wrong and forgot important paperwork the day we showed up to court" as that could make you liable for damages.

That's pretty much what bar associations are for, filing a complaint against an attorney at the bar seems like a pretty standard procedure.

>There should be a safe harbor for that.

A safe harbor would be the opposite, it would be immunity for the lawyer.

Even if there were it would just be another court case