Intellectual property demonstrably stifles innovation. It is the ultimate rent-seeking behaviour. It's not limited to software patents either. Hell, it's not even limited to patents.
The Wright brothers had a patent on the flight control mechanism that they used to stifle innovation [1]. This problem was so bad that when the US entered the First World War, they were completely unable to produce any aircraft and had to buy them from the French. This ultimately led to Congress intervening to form a patent pool for aircraft patents, a system that persists til now.
In the early days of the Internet (ie Napster and Limewire era) there was a lot of hand-wringing about "stealing" music and how it hurt artists. Almost no artist makes sufficient income from music royalties. Only the very top do. The rest make a living from perfrmances and music IP doesn't impact that. But it does help record companies to explit artists, which is the main point.
The pharmaceutical industry claims patents are necessary for drugs. Thing is, most drug research is undertaken by government funding and then basically just handed over to Big Pharma, who spend most of their money on marketing not R&D. What R&D they do is largely to game the patent system to extend patents without minor but irrelevant changes.
Copyright law is repeatedly extended (in the US) largely to stop Mickey Mouse entering the public domain. At this point I'd be happier with a carve-out specifically for the stupid mouse and let everything else fall into public domain
We do not need intellectual property. For atistic works, 10 years. Max.
[1]: https://en.wikipedia.org/wiki/Wright_brothers_patent_war