If you make shoes and I start making shoes, your shoes are now worth less due to my competition (increase in supply), but I haven't done anything wrong.
this only works if you start making different shoes. legally you wouldn't be able to duplicate the shoes and just sell them as they would be considered counterfeit.
the only reason this is justified, is because only the biggest players can produce the shoes cheaper than the original manufacturer, the power slips up if you allow copying, only the bigger players can out produce the smaller ones.
however, if everyone was capable of making shoes (or for a much better example, following a recipe to make a meal), that would mean the power slips more towards the consumers and smaller players (like the professionals in the industry, for example chiefs), which IMO, justifies dropping copyright (like how there is no copyright for recipes) copyright is to avoid monopolies of power to allow the free market to encourage innovation, at the expense of the other smaller players having flexibility with content.
if that copyright is preventing a slip towards empowering the smaller entities (who innovate much more than the big entities) to maintain the monopoly of the biggest players... its sort of exactly the opposite of what we want to achieve with the laws.
100% agree with your point though, nothing morally wrong with copying a pattern, you don't need to owe someone something because it already existed elsewhere.