It's true the Slicemachine is in beta at the moment and we are working very hard at making the Developer experience as smooth and easy as possible, this was the reasoning behind our creation of The Slice Builder and defining Slice models in your local project to push to Prismic.
The idea being like you said that developers will only really work through the CLI in that case.
In regards to the state of the CLI, I would say it's in very active maintenance, we had 4 team members working on it this week actually . Most of the issues in the git repo for the Prismic CLI were opened by our team and basically all of them were resolved with the latest update. The same goes for the PR's these are nearly all from our team.
Though I definitely agree that a change log could massively improve our communication and it is something that we have been discussing. So I'll push this further.
The latest change that we made was a tricky one as we wanted to play it close to our chests in communicating exactly what we had been working on and like you said it was an internal API change for Slicemachine users. So in the future we'll try our best not to communicate on big changes in the project.
Again sorry for the inconvenience this has caused your team and I hope you enjoy these new features that we've released as they should really improve your development workflow.
Simply update to the latest version of the CLI to begin using them straight away:
npm install --global email@example.com