PAPI don't provide guidance beacuse the midday sun floodlights them or they are notam'd U/S.
The advisory lateral and vertical guidance derived from RWY THR and calculated as a 4.5 mile fix at 1500' on the extended centerline is a valuable tool and very easy to use properly, without upsetting any gods of visual manouvering. Repeated references to RNAV + armchair uncover insufficient understanding of available technology and their use from your side, safetypee.
At JSI, most of the time it is the best tool to guide the plane to a point from which standard training and skill can take over. If you think pilots can eyeball A320 size CAT loosely unhinged in the 4D airspace somewhere between 3-9 NM in a sector 120-30 degrees offset from the final course - that's an invitation to a world of whole SMS review at the operator.
Or perphaps I couldn't decode the your message properly.