Proof by assertion
There are some assumptions here that need some justification. For example "If we have no protection of originality, then we get too little innovation." If that's the case, please explain the success of the fashion industry and the ubiquity of celebrity chefs - fashion and recipes are two things that have no "intellectual property" rights protecting them, yet they continue to support huge industries. There's no sign that people have stopped designing new clothes and new ways of decorating our bodies (there never has - do we still wear animal skins?) or thinking up new ways of combining foods.
And what about the near certainty that several people will have a similar idea at the same time (because they're all building on others ideas at the same time - nobody lives in a bubble). Someone gets to "own" an idea that someone else laboured over independently. That's a sensible system that rewards inventors?
The idea that people will stop having creative ideas because they can't stop someone else using them for 15 years (or for 70 years after they have died) is laughably untrue.
All patents have ever done is slow innovation down and hold us back. Or generate money for patent lawyers.