We do have such sites though, like Tom's Hardware or Consumer Reports or Wirecutter or what have you. Consumers pay money for these ads to reduce the conflict of interest, but companies still need to get their products chosen for these review pipelines.
Tom's Hardware and Consumer Reports aren't really about ads (or at least that's not what made them popular). they were about trying to determine the truth about products and see past the lies told about them by advertising.
Strictly speaking, isn't advertising any action that calls attention to a particular product over another? It doesn't have to be directly funded by a manufacturer or a distributor.
I'd consider word-of-mouth a type of advertising as well.
To me advertising isn't just calling attention to something, it's doing so with the intent to sell something or to manipulate.
When it's totally organic the person doing the promotion doesn't stand to gain anything. It less about trying to get you to buy something and usually just people sharing what they enjoy/has worked for them, or what they think you'd enjoy/would work for you. It's the intent behind the promotion and who is intended to benefit from it that makes the difference between friendly/helpful promotion and adversarial/harmful promotion.
Word of mouth can be a form of advertising that is directly funded by a manufacturer or a distributor too though. Social media influencers are one example, but companies will pay people to pretend to casually/organically talk up their products/services to strangers at bars/nightclubs, conferences, events, etc. just to take advantage of the increased level trust we put in word of mouth promotion exactly because of the assumption that the intent is to be helpful vs to sell.
