Are aircraft still guided by ground marshals?
Typically, marshalling is used to guide aircraft to their parking stand. 

There are alternatives available (Visual Guidance Docking Systems) that allow pilots to park their aircraft at the right spot without the aid of a marshaller. 

In its simplest form, the parking spot has a big identifier to allow the pilot to select the right stand, a centreline for the nose wheel to follow, a marking where the nosewheel should stop and a mirror so the pilot can see where the nose wheel is relative to the marking.

In its more advanced form, there are pressure plates in the stand that determine the position of the aircraft, a laser scanning system that determines the exact position of the aircraft and whether the stand is obstacle free, and a digital display guiding the pilot during parking. 

In case the VDGS is not available or cannot handle the specific aircraft type, a marshaller will have to step in.