@nflanders Re focusing on the majority, more than half of FAF games are against AI. FAF provides numerous AI, including both an improved default AI and various different custom AI (https://wiki.faforever.com/en/Development/AI/Custom-AIs).
So if measuring by the type of games played a lot of time is already spent on the majority.
FAF is also welcoming to people who want to volunteer to develop features so if someone wants to fix one of the various issues noted for the game, or create their own mod that implements their particular vision, they can. FAF is also supportive of such efforts with significant increases in documentation, tutorials, and the availability of support from various other FAF volunteers to help with questions/issues.
As for why developers are volunteering their time to develop certain features such as the matchmaker, that'll be a matter for the person in question and I wouldn't want to speak to them (although I'm very grateful that they have implemented such features and many others). Since we're talking about volunteers though ultimately it will be down to the volunteer what to focus on - trying to force volunteers to look at something they dont want to is counterproductive and will just lead to fewer improvements to FAF.