I’m also pretty sure that on an episode of The Standup, one of the Neovim core maintainers TJ DeVries (Teej) said that it is a good idea to prove new ideas in the form of a plugin rather than submitting pull requests for Neovim itself with new ideas that have not yet been tested out and proven in the real world. Implicitly implying that indeed Neovim is open to bring features from plugins into core Neovim itself, if they are proven to be useful for a lot of people.
Unfortunately I don’t remember what episode it was or even if it was specifically on an episode of The Standup, or if it was some other video that he and ThePrimagen did outside of The Standup.