I can definitely see your point, having experienced the same thing with plugins for SBT, the Scala build tool. I didn't really consider the case of a small core with a multitude of plugins as a twist on the small, simple tool. I think you're right that a plugin architecture lets a thousand flowers bloom, but you don't get long-term stability, because people move on to other tools and stop maintaining the plugins they wrote.

For example, VSCode plugins are great because VSCode is thriving, and Emacs packages are a crapshoot because many of the programmers who wrote them have moved on. Eventually VSCode plugins will be like Emacs packages.