Quoted: "From a vertical guidance perspective:
LNAV -- no vertical guidance. Does not require WAAS.
LP -- no vertical guidance. Requires WAAS.
LNAV/VNAV -- with vertical guidance, using baro-VNAV systems. WAAS may be used instead of baro-VNAV.
LPV -- with vertical guidance, using WAAS. (WAAS required).
GLS -- with vertical guidance, using GBAS."
Nice summary. Still, all provide guidance in the instrument segment to some minimums - MDA, DA or DH - and the pilot must make a decision to continue descent and operate into the visual segment to land.
The pilot must be capable of making a safe decision and skillfully use the flight visibility and visual references to visually control the airplane to land. The main problem, as I see it, is safely conducting the visual segment which means, to begin with, not accepting less than then necessary visual cues. The safety of every instrument approach, except Cat III autoland, requires this.