Headless browser scrapers might blacklist things they don't need, like ad domains and trackers, since all they do is slow down how long it takes for their desired content to load.

The algorithm simply checks to see how often you check in with Google and how "human" your actions are based on the data you send to them via things like Search, Maps Location History, YouTube, Gmail, probably Chrome Sync, etc.

If you're using a completely new Google Account and block all of Google's Trackers, choose to use FastMail for your actual email communications, and only occasionally watch YouTube, Google has every reason to believe your IP is a residential proxy that's being used by a bot or perhaps someone in a third world country working at a recaptcha farm. They can't completely prevent the latter from solving their Captchas but at that point all they need is for the farm worker to help Google tune its self driving dataset.