>I, personally, believe that the whole point of ads is to manipulate you into making purchasing decisions that are irrational,[...]. Therefore I think all ads are unethical.If I invent something I truly believe will improve the lives of others that they might pay for, how would I let the world know about it other than ads?
Examples...
I'm wearing $350 noise-isolating earphones at this moment because I learned about the product from an ad 20 years ago. There was nothing else on the market that combined audiophile sound quality with 25+ dB ambient noise reduction. (It was a small company that specialized in hearing aids that expanded their product line into consumer hifi.) I wouldn't have learned about them through "word of mouth" because nobody I knew had them. I loved them so much that I've bought 3 replacement pairs over the last 2 decades as they've worn out. That ad for earphones saved my hearing and sanity at noisy offices.
I applied to the high-paying job that paid for my house because of an ad the company ran looking for my particular technical skills.
I went to performances of classical symphonies and piano recitals because of ads highlighting the local orchestra and the upcoming season's schedule. I also went on memorable helicopter tours because of ads.
Yes, _most_ ads (including most Youtube ads) are harmful/intrusive/irrelevant but saying _all_ ads manipulate you against your best interest can't be right.
>in theory an ad could be designed to be genuinely useful
It's not theory though. In my case, my earphones/job/concerts were genuinely useful to me. Unfortunately, it's the minority of cases where ads connect me to products that improve my life. Therefore, I do block all ads at the DNS level but I'm still receptive to ads relevant to my interests like 3d printing, home building & construction, aviation, etc.