More specifically with FOSS projects, whoever puts in the work makes the actual decisions.

Like, if there's a change that one person wants and the others actively disagree with (and it can't be made configurable either), then that won't happen.
But usually, there's hundreds of features that make sense in principle. And if someone scratches their own itch, i.e. implements the feature that they're missing, then that obviously won't be rejected, even if it's not the most requested feature.

So, yeah, such an idea guy would need really good ideas and present them so well, that others selfishly want to implement those ideas (and moreso than all their other ideas).