Yeah, if you're 5 idealists with the same dream you probably won't screw over each other too much, and whoever tries to set rules for everyone else probably will turn out to have some unpleasant ulterior motives for it. But large groups are very different from small groups, the dynamics are very different, and far more structure is needed for things to actually function.
Some people just have to learn that the hard way I suppose.
To summarize: it is a well-known fact that those people who must want to rule people are, ipso facto, those least suited to do it.
To summarize the summary: anyone who is capable of getting themselves made President should on no account be allowed to do the job.” (Restaurant at the end of the Universe - Douglas Adams)
Also, a NFT marketplace can't just ignore it forever. It's a .com, it's connected to a real person who can get in trouble.
Also, no, engineering is ultimately in the service of people and has to work with human constraints in mind, including economics and law. Like they say, “Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.” -- working under such constraints is why we have engineering, rather than just piling up bricks until there's no way for the bridge to collapse.
It's just that a marketplace based on at least theoretically selling unique copies of artwork can't really exist in this particular manner. Who made a given piece of art, and who has the right to sell it isn't an engineering issue, and makes no sense whatsoever to do in a decentralized manner.
It's about profit. Things like proof of ownership means more complexity and reduces profit.