Every CLI can be expressed as an API and vice versa. Thus every skill can be expressed as an MCP server and vice versa. Any argument about the technical or practical merits of one over the other is willfully ignoring the fact that you can always use exactly the same patterns in one vs. the other.

So it's really all about availability or preference. Personally, I don't think we needed a whole new standard with all its complexities and inevitable future breaking changes etc.