That would also preclude non-disclosure agreements. I'm curious if you also find those unreasonable?

Both non-disparagement and non-disclosure agreements should—just as many jurisdictions have for non-compete agreements, which do not even implicate free speech the way the others do—be sharply limited as a matter of public policy (non-disparagement even moreso than non-disclosure.) Both are routinely used to inflict public harm for private gain, and government enforcement of either is in tension with freedom of speech; while there is a legitimate case to be made that non-disclosure agreements within certain bounds have a certain degree of necessity in enabling legitimate business, this is a much harder case to make for non-disparagement agreements, at least for ones that are not temporally bounded within an active business relationship.

Depends on what type of non-disclosure. Disclosing technical guarded and not publicly known technical know-how - I am ok with those. Disclosing that boss treats people like trash should be allowed and I think lawmakers should have enough intelligence in their brains to make laws accordingly.