He doesn't mean that there's a barrier to entering the search engine business. He means Google itself, having so much power, is a gate-keeper, deciding through their search results what sites deserve to be found quickly by average users and which sites do not.
Google does discriminate. It must. There's only a finite amount of screen space on a user's device or display so a decision must be made to prioritize certain sites over others.
Some site even pay for that prioritization.