Your assessment of boat construction is correct and also unlike the GM/Honda example you gave the dealer plays a more critical role in warranty and after sale service.Never having bought a new boat, until I read this thread I was surprisingly naïve. I understand that aside from the hull and interior, most of the other things are outsourced. Still, they are shopped and spec'd by the boat manufacturer, and the research and design that goes into cobbling all this stuff together is part of what one pays the big bucks for. I also understand that unlike cars, boat manufacturers don't make enough units to establish the kind of national or international support we've come to expect from the likes of GM or Honda. Nor can they exercise the power carmakers have over their dealer networks. I also imagine that because selling boats is a lot riskier than cars, inducing a dealer to invest in carrying any particular line is a major accomplishment. All that said, if I plunked down the bulk of my retirement to buy a higher end production boat like a Ben or Jen, I would expect far better quality control and support than I am reading about here. I might accept a few minor glitches, and I sympathize, to a point, with the dealership's lack of enthusiasm for cutting into its profits to remanufacture the boat after sale (I'm sure they understand that like it or not the buck stops with them). I just can't seem to wrap my mind around how that would induce me to let the manufacturer off the hook for selling me a product that has serious problems compelling me in many cases to attempt the fix myself and imperiling my warranty.
I would do as much research into the dealer as I would the boat I'm intending to buy. Having said that our last 4 boats we've purchased including our last a B 423 have been new. We have been fortunate in that only a couple of minor issues cropped up - one of them four years after the purchase. Both were taken care of promptly and without cost to us.