There are about 75 individuals in the triage team who can close, open, label and tag issues on the issue tracker. Any one of them can take action — based on their own best understanding — what to do with any particular issue.
There are about 50 individuals with commit rights — the folks that can merge PRs themselves.
There are a handful that meet biweekly to try and unwedge issues that are complicated or that folks aren’t fully agreement on.
All of our individual motivations and priorities vary, but everyone tries to move through consensus. In many cases, the PRs themselves serve as the “enhancement proposal,” but for very large things folks have first collaborated on hackmd — for example Memory or Pkg Applications. Milestones typically represent release blockers and are more internal organizational tools than high-level goals.
So, yes, this is a ship being steered by lots of people, all trying to work together to chart a good path to improve things for everyone.
It’s far easier to talk about what a particular person (or group of people in the same company or org) are doing, but that is not the whole of the project. To see what JuliaHub is doing (I am a JuliaHubber), this recent post from July is very good: