You could add your mod to a site like Modrinth or Curseforge to increase user base.

I know, right now it is in BETA, but the mod is stable enough for daily use and there is nothing really stopping you from uploading it there.

I can understand, if you would prefer to delay it for release, just please consider it.

This is being done now.

One of the reasons they might not want to add it, is because that encourages people to think it will "just work", whereas this is more of a "for developers only" type of thing until it's finished.

They could just add [BETA] in the name or something like that though

Yes, the dev could just label that it's in an alpha/beta state.