For someone like myself who is not already a core Python maintainer, how would you recommend making improvements to things like the Python documentation if not by raising pull requests?
Otherwise, one could help in ways like I mentioned previously: reading existing issues, checking if they are still relevant and commenting accordingly, reviewing PRs and patches, etc.
That is precisely what I did. As noted, there has been no indication (by activity on the issue or PR) that having filed these helped or is appreciated. Hence discouragement.
It is one of the hard lessons of open source maintainership that, without providing feedback to contributors, there is no demonstration of the project's appreciation. Therefore new contributors will (correctly!) conclude that the project does not appreciate these efforts.