If airlines thought this was a reasonable thing, they could install barriers/curtains and/or include in their announcement that passengers should not congregate in galley areas.

I generally don’t hang out in the galley. I feel for FAs when some passengers feel they need to engage the FAs in endless chit chat in the galley. I rarely go to the galley to ask for a drink or snack. But it can at times be unavoidable to use the galley space to wait for lavs to free up. FAs know that there is no private space for them (or passengers) on an airplane when they sign up for the job (assuming they have flown before).