How not to ...
"Google's Performance Max tools will analyze a supplied landing page to generate appropriate headlines, text descriptions, and images to use in Google-served web ads"
The essence of good advertising has always been creating a message that strikes an emotional chord by saying or implying much more than just headlines and descriptions can offer. The proposed approach is highly unlikely to be able to produce anything but the most banal and ineffectual advertising. But of course Goooooooogle won't care whether it's effective as they get paid even if it's not and it's pretty hard for the advertiser to pin them down. The well documented poor return for advertisers on the current auction based ad placement already demonstrates this. The problem of course is that nobody dare not advertise these days, so lousy is safer than none despite the cost.