So I can tell you from experience that there's a huge difference in terms of how much of your products you sell by doing advertising versus doing nothing. It's very rare that advertising is designed to take the person who's observing it from "IDK what this is" to "Holy crap I gotta go buy that" -- but building brand recognition, making people aware that your stuff exists, and yes sometimes having them see an ad for something and click on it and buy something, is 100% worth it when it's done right.

I actually do agree with you as to as lot of advertising on the modern internet, though. I think like a lot of areas of human endeavor, online advertising has been overrun by people who genuinely just have no clue what they're doing. Someone works at a company that has a river of money coming in, their job is to buy online ads, so they direct some of the river of money at buying obnoxious ads that do very little except piss people off (and, enable the site where they run to keep operating and paying their people, which is nice). It doesn't accomplish anything for the company they work for and no one notices, and that persists for years, and the internet as a whole is crapped up for everyone in general. :-/