While I think the hobby is getting to the consumer level standards, particularly in the multirotor realm, I don't think the fixed wing part of this hobby is nearly there... yet. Some of those advances are coming, but making products consumer friendly sort of assumes a very low common denominator for skill levels and experience.
Even now, when I stock up on RC components for builds, etc, if I need 4 servos, I buy 8. I've experienced first-hand servos that don't work out of the box. I tend to buy the cheap ones, so I know what I'm risking and taking the gamble with that just to be able to use $2-3 servos.
There has always been a difference at the consumer and hobby level though. I would would the consumer and hobby grades to buying a franklin mint diecast airplane model (pre-finished) or buying a plastic model kit. As with any hobby, there is an expectation that the consumer has enough knowledge and skills to finish the project. The multi-rotor is more akin to the prefinished model, especially if you use something like DJI as an example. You just pull it out of the box and go.
It isn't that much different in Fixed wing and heli markets, or in the mini quad market. You as a consumer are assumed to have the knowledge base to check that everything is working as it should, and to research the aircraft before you fly. That you will do meticulous pre flight checks, and take your time getting your control settings dialed in as required. If you find something, like a dead component (servo, ESC, retract), it is the responsibility of the seller to replace it. And, MotionRC does that quickly and reliably.
From a standpoint of quality, it is the nature of hobby grade components that quality is never perfect. We are a tiny piece of the market, and things have to be produced quickly and affordably to sell. Let's say a manufacturer revamps their servo quality checks. Like most RC companies, they probably do a cursory check to make sure the servo moves, then install it. Let's say that is changed so that each servo undergoes 15 minutes of continuous cycles and the speed/throw tolerances are measured before and after. You have now easily quadrupled your time, and you produce less . Now cost is increased, and instead of $6/servo, you might be looking at $20/servo. Multiply that times 9-12 servos, on a big warbird, and you've ballooned your cost by $140ish. Now that is priced so high, it doesn't sell well or isn't competitive with other models. And, you haven't gained much either. Instead of 95% of servos being fine (basic check), you've brought it down to 99.9%. Or you could just eat the cost of any failed components, and sell at a competitive price, which is what Motion does. For the record, I've had 10+ airplanes (large jets/warbirds) and I've had 1 servo and one retract that were bad, and they were promptly replaced. That's not a bad record over ~100ish servos. As with anything there has to be a balance between cost and quality to make the business feasible.
As for the manuals again, they are written by the manufacturers at whatever rates their test pilot likes. If he likes his Mirage to roll like a drill bit, then that's what ends up in the manual. When Motion works with them on design, they provide feedback on the design, and send it back to the manufacturer to revise. The manufacturer completes these revisions, and Motion re-evalutes it. The design is done by them, with guidance from Motion. The manufacturer still produces their own documentation, and that's what goes in the box. At least the Motion reps on other forums such as RCG have been kind enough to post the rates/cg that they preferred flying at as well for reference.