Game engines and servers are great candidates for developers to collaborate their ideas into FOSS projects, but the model is harder to sustain for complete works.
While internet games can have subscription models where you pay them for doing game master type activities, moderation, and access to a hosted game server, static games are more like static art where you run into issues getting food and housing when you make your work output available for free. Crowdfunding / patreoning (in the larger sense of the word, not necessarily the app) creators / collectives can be a way for that to work, and we need to support more creators trying that model if we want to see more of it.
I haven’t used Pixelfed, but does it fail to work with with microblogging fedi platform content so bad that you feel you’d have to use Mastodon? Outside of the group/community/threadiverse federation issues in Masto and Lemmy not letting you follow accounts, I my understanding was everything worked pretty well talking to eachoter.