I think there is a trick that could be used in this case, which would not require re-categorizing all the items.
It would require creating another field below the "Search for item" field in the market page, something named "exclude items" for example, so we could use words to define which items we want to exclude (for example, "knuffel" for wild knuffel items).
Spoiler: Technically speaking
In short:
I meant that to the existing SELECT FROM Database WHERE DBItemName = FormField clause we would add a AND DBItemName != ExcludeFormField condition.
Not that
I would use it much, to be honest, cause I like browsing the marketplace so I don't mean to be seconding the request, just throwing an idea which could help in case you are interested in adding such a feature for the market without creating a new category and all the problems it would mean.