The first step is data minimization. The second step is informed and revokable consent. Everything else follows from there.
Do targeted ads increase the amount of personal data that needs to be stored and processed and the number of entities that will access it? Yes they do. Are they required for the site to serve its stated purpose? No, unless the site is marketing itself as literally a curated stream of targeted ads. So they require informed and revokable consent (i.e. opt-in). Even if you think they're beneficial to the user.
It's not about what's beneficial. It's about what's required. That's why most sites try to group services by categories like "functional", "analytics", etc. If you want to embed a Google Maps view to help people find your physical store, that's beneficial but still requires consent because it shares their data with a third party (i.e. Google) when the browser loads that map. Of course in this case you don't even need a banner, you could just have a placeholder (often called "content blocker") instead of the map with the option to consent to loading the map and storing that decision so the user doesn't have to see the placeholder again.