There are plenty of plastics already developed for protection from UV light, the RV parts manufacturers are just not using them for many things.
Windows for homes come to mind, as they are made from uPVC, and hold their colour very true. With time there is a bit of oxidization that happens, but a bit of a polish can take care of this.
Along the line of windows and doors. Have you ever seen the plastic trims on door inserts that turn an ugly yellow over time. This is because they are meant to be painted, and the uPVC plastic does not take most paints very well, and many home owners don't bother to paint to protect.
So I think the onus should be placed on the manufacturer of these parts, to use a plastic that has UV protection built in. The technology is already there. Whether they are c heaping out or not, or just hoping you have to buy replacements, I don't know, but I agree that they do need to start building better components.
To some degree I think the blame lies with the consumer, who does not want to pay the costs of better quality components, and if they did, all trailers would start costing closer to what Airstreams cost. No different then how everyone knocks Chinese quality in items. It is not the fault of the Chinese, we are the ones that want these items at ridiculously cheap prices. They have the technology to build with top notch quality, it just costs way more to produce.
2017 Escape 5.0 TA (someday soon, I hope
2015 Ford F150 Lariat 3.5L EcoBoost
2009 Escape 19 (previous)
“Most folks are about as happy as they make up their minds to be.” — Abraham Lincoln