It is useful in specialist domains. If you love fashion then fashion magazine ads are worth studying,
because you read them with a critical eye. If you're into any sort of nerd hobby (model trains, synthesizers, board games...) then the specialist magazines/video channels/forums for that hobby are interesting, again because you have a critical eye. Sure, there are ads that target the newbie with 'the first and last ______ you'll ever need!' but as you get more experienced in the hobby you quickly learn to distinguish which manufacturers are selling the dream vs offering their product. This remains true even on forums for particular vendors that have a cult following. Likewise for many professional trade news outlets.
But it only works where you have specialized focus and experienced/informed consumers that are able to separate the sizzle from the steak. For example, doctors and other medical professionals are generally well qualified to assess the claims of pharmaceutical advertising, consumers are not - even though I am comfortable reading the fine print in such ads and even reading papers about clinical trials, I still rate my evaluative ability as mediocre compared to a professional.
Mass market advertising for general consumers is generally cancer, imho.