AFAIK automatic landing systems just get the plane into the right 'landing parameters range', but won't take action if anything unforeseen happens (like a blocked runway).

Right the Garmin Autonomi Autoland system is intended only for emergency use to get the airplane on the ground if the (single) pilot is incapacitated. It's not intended for routine autonomous flight.

I think the earlier comments are referring to CAT 3 auto land systems using technologies like ILS, which are used routinely and are good for 0ft visibility. That is, approach in cloud down to the ground