This has been our experience running an ad network that only does content-based targeting (https://www.ethicalads.io/). As noted in the article, simple heuristics and topics are plenty to target ads, and provide great value for both advertisers and publishers. We're also cutting out all the ad tech middlemen who take a cut, keeping the value in the developer ecosystem, and keeping the web more private & secure.

We basically let someone like Sentry or Twilio target JS developers with a specific ad about their JS integrations. They can link to JS-specific landing pages with sample code, etc. It works super well, and doesn't require anything beyond knowing the content of a page.