Being able to build high quality software alone is a distinct skill from being able to make a group of engineers productive. Neither are soft skills, it comes down to how the software is architected and how well you can produce, understand, and communicate designs with the other collaborators.

I do consider helix to be an impressive piece of software, and I agree that the user base is growing, not necessarily the set of effective maintainers though. The maintainers don't seem to have any aptitude for coordinating engineering effort. That would be fine, if they were honest and direct about it. SQLite is a project which does not accept contributions, I think helix should do the same.

Put differently, I don't expect the large community to have a meaningfully positive effect on the quality of the software, because the maintainers have not demonstrated the competency to effectively utilize that labor. I expect helix to continue slowly improving at whatever rate the maintainers can make important changes themselves.

It’s a ridiculous and inflammatory claim to make about a clearly successful project with an enthusiastic community of users who love it. The maintainers have day jobs and have a clear and narrow vision that they don’t want to mess up by carelessly expanding the pool of maintainers. That is the entire explanation!