Why can't an agent outrank the listing portals?
Because those sites have every listing in the country, update constantly, and have twenty years of accumulated authority. That search is lost and it shouldn't be contested.
The listing search is a portal's core product. An individual agent competing there is spending money on a fight decided before it starts, usually via an IDX feed that generates thousands of near-identical pages — the exact thin-content pattern that damages the rest of the site.
What isn't lost is everything the portal can't do: judgement, local knowledge, and answers to questions that aren't 'show me houses'.