On reflection there have historically been some "do it better" moments, but these have been in the build technology rather than the execution/quality control of the process; notably here Elddis development of their bonded system "Solid", Bailey's into their permutations of "Alu-Tech", and Swift briefly into their bonded woodless system that they offered for a while before pulling it.
All sadly IMO let down by the sloppy attention to doing the build executions properly time after time. Plus, the contractual model they have with their dealers and that in turn playing through to how they treat their end customers.
A lack of interest in where the money really comes from and with it, at least in a normal market place where there is a need to be attentive to "please". However, on this last point, "a normal market place" UK caravanners collectively seem to buck market normality and be content to buy into the same deficient issues repeatedly.
Technically on top of all this, again IMO the adoption and steadfast retention by some with the use of ABS plastic for integrity critical body items where failure levels are so high because of the inherent nature of the product. Particularly its aging, degradation from UV and intolerance of stressing, make for high levels of water ingress damage to the van's critical structure. Basically, used as it is designing in high levels of failure. As elsewhere ABS can be used to good effect for styling finishers, but only where they play no part in the integrity of the product itself.
All said, IMO they face having the wrong product for the emerging market, we simply will not be able to lug our ever bigger boxed home from home around in the not to distant future. New products or a disguised reincarnation of an old one will be the only products viable in a mass market.