DRM is fundamentally about controlling what you can do with a computer you own.
No. DRM is about controlling certain items of content. It’s data. It doesn’t have squat to do with how you use your computer. The hardware, OS, and application software is not affected.
Even advocates of DRM admit that this reduces freedom.
Of course it reduces freedom, overall. That’s kind of the intent. It’s a swap so you can get your content creators paid.
They mostly argue there is a corresponding economic benefit (there isn’t)
If you say so. The goal of DRM, obviously, is to protect copyrights. If it doesn’t succeed in doing that, then yea, let’s move on to something else that works.
But until we have that “something else”, don’t get annoyed when content creators want to get paid for their work. That’s kind of fundamental to the economy.