You are incorrect. Not in "most cases" - but in many, yes. However, putting more plumbers in your bathroom will not clear that clog any quicker, relatively. Having more cooks in the kitchen can create a cacophony of a mess if the work and space does not demand it. Every job/task/project has different requirements for effective progress and continuance of said job/task/project.
As for this independent game - Breadman is the artist and is the only one who they are willing to trust to do the art. The same can be said for the other roles. If you bring on more people to help with art, Breadman moves away from the work he loves - drawing and moves more into management, which he may (or may not) despise. This would affect his morale on the project. This would also introduce more conflicts. Such changes may actually hinder progress instead of expediting it.
Again, looking at his subscriber numbers - it appears that he has a lot of support for what he is working on and how his is working on it from the people who drop a tip regularly in the jar for him to continue. If they start to dip, then the team may decide to change their strategy, until them, we will just need to wait.