I'm sure there's a niche for a product for search nerds. Something that leans into inverted indexes like the classic Lexis/Nexis search. But it's got to have Google-like coverage.

Niche + Google-like coverage is not very economically viable. To store and update a search index of that size requires a lot of resources, and being niche means you don’t have a lot of resources.

Very few of the smaller search engines actually do their own indexing for exactly this reason.