arguably, that's a good thing because it means project decisions are made uncorrupted by profit motive

Argue-er here, chiming in. This statement could be interpreted as considering only half of the central relationship of capitalism. (Capitalism isn't just about deriving profit from the control of surplus, it's about the relationship between surplus and scarcity. Surplus doesn't mean shit if no one wants what you have.)

The decisions that volunteers make may not be motivated by the desire/ability to make profit, but they can be (and often are) motivated by the opposite; they have to account for the fact that their volunteer work is labor that isn't contributing to their survival -- aka, their day job. The demands placed on them by their other responsibilities will have to take precedence over the volunteer project.

In practice, this means they have to take shortcuts and/or do less than they would like to, because they don't have time to devote to it. It's not exactly the same end product as if it was profit-seeking, since that can tempt maintainers into using dark patterns etc, but they're similar.

Ideally, they would have all the money they needed, didn't have to have regular jobs, but also had families/friends/hobbies that would keep them from over-engineering ffmpeg.

To say this in a simpler/shorter way (TD;DR), their decisions can be motivated by the fact that they aren't making money from it, don't have enough time or resources to do everything they might want.

(Why is this so long?? I'm bored in the train, gotta kill the time somehow..why not say in 1000 words what I could have said in 100)