My requirement is user-respecting. Software should respect users, be useful to society, and should not (be designed to) cause harm (environmentally, psychologically, should respect user's privacy - and why this is important is its whole own discussion).
Free software is (arguably) a requirement for being user-respecting. A necessary condition. Because it is theoretically necessary for users (or someone they ask - most people don't have the required time / knowledge) to be able to adapt or maintain pieces of software they rely on, if its original builders ever disappear, want to take another path or simply won't fulfills the user's need. Because the users should be able to inspect their software. But indeed not sufficient. You may need guidance to understand the code and build it (documentation) [1]. You need reproducible builds (so someone can check that the shipped version does what the code says, so users don't need to build the program themselves each time to be sure). And other requirements too: like the software should not manipulate the users to make them do things that they would not have done and cause harm, or skew society in some undesirable direction. Which can be subjective.
For instance, Chromium is free software, probably documented quite well, but still serves a monopoly from an ad-supported company, which is arguably "not sufficiently" user-respecting and helps it to push the entire world to an economical model that relies on user-privacy issues, manipulation caused by ads, and control from a company bigger than countries and yet not democratic at all (assuming democracy is desirable).
Software should be free. And more. How exactly? I don't really know.
[1] Note that I also think we can't require documentation or any extra work from people contributing free software neither. They already make a gift to the world by releasing their free software, especially if they do it in their spare time.