Buy a Honda Accord and you can expect pretty good quality, while both a Kia and an Aston Martin are likely to disappoint you with quality. Likewise, a box of plastic 40K models are likely to be flawless, while your experience with Forge World or Battlefoam might require some compromises. This is not to excuse their quality problems, just to explain that the cutting edge is called that for a reason.
As our hobby matures, we hopefully can see the same type of improvements that the auto industry has seen, in which almost any car will provide you with reliable transportation. The goal is to steepen and narrow that bell curve of quality. I think we're already seeing this with mass produced plastic models.