When Google adwords first arrived on the scene, I tried them out. But the idea was that the ads would be contextual to the content on your web page. So if you were writing articles about gardening, your ads would be about gardening implements. If you were blogging about education, the ads would be about schools and places of higher education. You get the idea.
Me, I was the idiot writing stories based on the Ramayana. Fat lot of good the adwords program did me. My sidebars were full of ads for gardening implements and places of higher education. Nobody clicked them. And the little I made as a result of ad impressions was... well... little.
I smile whenever I see an ad for an ad program that shows a smiling person sitting before a laptop because they "make money from their blog". It does not happen. It has never happened for anyone (at least in the ways the thing is sold to us). Even people who did make decent money from ads decided they could not rely on it and went in other directions. Most prominent bloggers of the early 2000s are now running their own premium subscription programs.
The current web generation does not mind paying for content on the web. Platforms like Newslaundry and The Ken are good examples. Plus, there is also the matter of people having become ad-blind. When was the last time you knowingly clicked on an ad on a web page?
If advertising was completely useless, no one would use it. However, as far as monetising creative content is concerned, it is about as effective as expecting money to rain down from the skies. Targeted ads can work wonders for your brand recall, but they will not help you sell enough to sustain yourself.