it is indeed one of the many ways to learn a project, what I think by advertising on popular sites is that those who want to start a project have capital. not only want to create a fake project without using capital. maybe it's one of the easiest ways to tag, but there are also a lot of bad projects that appear in ads on popular sites.
I do believe that just because one project has a lot of marketing doesn't mean that it will definitely end up being a good project, but I also believe that a good project without marketing will not grow big neither, even if you end up hearing about it, if others do not hear about it then it doesn't matter. Which is why I believe that marketing is a must, bad or good it has to have big marketing and that is when we can start to look at it differently.
I have seen so many non-scam projects that ended up being absolutely a disaster just because they couldn't do marketing properly. I was even part of a project that should have been basically a top 50 coin and right now it is not even in the top 3000 just because they lack funds and they couldn't do any marketing at all, they are good people building a great thing and nobody knows about it at all.