Ultraviolet light breaks down the top layer of clear coat. The finish goes chalky, colour goes flat, and no wash brings it back.
This page explains oxidation, how the valley's sun speeds it, what correction can restore, and the point at which the clear coat has failed and paint is the answer.
Ultraviolet light and heat degrade the polymer layer that gives gloss. The surface turns opaque at a microscopic scale, which reads to the eye as a dull, chalky finish on the roof, bonnet and boot lid first.
If the clear coat is intact, polishing removes the degraded layer and exposes fresh material. If the clear coat has peeled or blistered, the paint system has failed and no polish fixes that; repainting is the only route.
Yes, if the clear coat is still intact. Machine polishing removes the oxidised layer. If the clear coat has peeled, only repainting will fix it.
Park in shade where you can, wash the dust off regularly, and apply a ceramic coating, which starts at $700 locally.