Is this coming full circle: Git -> GitHub -> GitHub CLI?

CLI or not, it's centralized/siloed all the same. I'm sticking to Git.

It would be really nice if the other features of github could get into the decentralized model of git... I could imagine issues and PR reviews/comments all being mini-commits to some kind of parallel metadata repo under the hood for example.

There are some experimental tools for distributed code review and issues.

https://github.com/google/git-appraise

https://github.com/dspinellis/git-issue

Would be nice to have something more polished though.