The biggest piracy sources that authors have trouble with are the ones in places like Middle East, Russia and China. DMCA has no meaning there and they have no treaties with American companies so there is not much that can be done in fast pace with local authorities or in general, at all. If you were a seller and maybe had access to the various private groups you know this. Unity legal team has blocked many of these sites from search engines but they are still limited when it comes to take down the sources. Same problems are affecting Epic games and you just might not notice it cause it’s not as widespread problem with the marketplace content yet.
You can easily waste $5000 if you cant program at all and do not have the experience to produce stuff specific to your requirements. It’s not like that every Unity user is throwing cash to the screen because they and helpless without em. It just looks like that the general trend seems to be today that if you don’t have visual material editor or scripting the users are ****ed up and cant progress, if there is feature x missing they cant progress. In reality there are plenty of people who can still for example produce shader code easily or code the stuff they need.
For the header and conflicting code have you ever heard of namespaces? it’s been pretty rare to have conflicting assets for quite some time now and depending of the asset type and scale they get rejected without using one.