Fine dust, dirt and sun are the enemies of car paint. A car paint that is not maintained (especially red paint), will chalk. A dull layer is created on top of the paint. That dull layer becomes thicker if nothing is done about it.
Can't save lak anymore? Polish anyway!
If the paint is in such a bad state, there is not much that can be saved. But you can always polish the paint or have it polished to get a better result. Only it will take a lot of work and it will continue to gamble how well the paint will recover. Maintenance is then also more intensive than with a good paint. Luckily there are specialists today who can often repaint your car paint up to 85-95% of the factory gloss.
It may take a day of work with special machines and special means, but it is still considerably cheaper than having the car repainted.
So keep the paint clean and do not park your classic car in the full sun, but enjoy the sun yourself!