> What makes a senior engineer?

Nothing in that article. It only means the person (probably) fits the 8 or so bullet point skills that management has said a senior engineer needs to have. And it's company specific.

If you want to be promoted, then either, ask your manager, or apply for a senior job somewhere else.

I don't get how these articles get so much traction. They are like fortune telling, just spout off some non-specific high-level items and let the audience fill in the blanks.