Also, ProseMirror is definitely seeing wider adoption than the parent implies. Even from this thread alone, we're seeing Atlassian and startups pop-up attesting to its good design.
Your points are fundamentally correct, and I would argue that your parent is attempting to limit the potential of ProseMirror, in order to preserve the need for Quill.
Your points are fundamentally correct, and I would argue that your parent is attempting to limit the potential of ProseMirror, in order to preserve the need for Quill.