Has camper quality gotten any better in the last 10 years?

Some of it is they are hitting a price point.

Much of it is expecting automotive or household quality:
- Autos are produced by the tens of thousands. They have comparatively very little modification from unit to unit. It's far easier to set up quality control.
- Houses...when was the last time you hit big pothole with your house at 60mph?

Sealing is just regular maintenance. Keep things sealed up and it should be good for a very long time. Let things leak and expect it to be trash in 5-10yrs.