Recently, a friend let me paddle his plastic kayak, a boat that he was quite fond of. I never turn down an opportunity to try out other kayaks and so I got in this one and paddled away. The boat looked very pretty with its white bottom and yellow top and was still new and shiny, but the bow seemed too blunt and pushed too much water, creating much noise in the process. It wasn't a flaw that you would be likely to notice just by looking at the boat, but it was readily apparent once you paddle it.
I reflected on this and came to the conclusion that I couldn't be the only person that noticed this problem with that boat. But given that the manufacturer had already invested in a mold, he probably had to sell a certain number of boats before he could recover the cost of the mold. Only after that point could he consider making a new mold. The longer he held on to the old mold, the cheaper the cost per boat would be.
And that, in a nutshell is one of the major problem of mass produced boats. The thing that makes mass produced boats cheap is that they involve a minimum of labor. Make a mold, and once you have a mold, you can squirt plastic into it and out comes one shiny boat after another. But the mass production is a good thing only if you have designed a good mold. The manufacturer had better built a number of prototypes and tested them for good design before committing to a mold.
If users give the manufacturer feedback on design flaws, he really can't do much until his first mold is payed for. And this is more of an issue for small manufacturers who, lacking deep pockets need to pay as they go.
If you buy a custom boat from an experienced builder, you pay more than for a production boat, but you are also less likely to be a victim of design flaws. I suspect the custom builder gets to build a lot more boats and gets a lot more design experience than the builder of production boats. I might be wrong, of course, given that I don't really know what credentials production boat designers have or whether production boat manufacturers even have experienced designers on their teams or just hire consultants or copy someone else's designs. If anyone knows, I'd like to hear from them.