Webpages used to have meta keyword tags until spammers hijacked them for irrelevant keywords.

I think browsers can play a part in building a local search index for URLs based on those keywords the page declares and cross verify/accept only those that are in prominently visible content, or may be delegate to an external engine(like LLMs) via an extension etc. This is particularly useful for cases where full text indexing is not feasible or desirable.

I doubt Google will ever add such feature in chrome though.