Relevant/personalised ads doesn't mean ads that benefit you. It's means ads that are better able to extract money from you.

It means that, when you need a new dishwasher, you will never see the actual best dishwasher for you, only dishwashers that are a bit more expensive than you actually need but you will end up buying one of them anyways.

It means that you are more likely to see products you would impulse buy just after you get your paycheck. Or slightly inflated prices on things you usually buy.

It means ads designed to take advantage of addictions to sugar, alcohol, gambling etc

Finding stuff you actually want to buy has never been easier, you can find hundreds of reviews and comparisons instantly. People who opt into personalised ads don't end up being more savvy online shoppers, they just end up buying more junk.

My preferences are based on my understanding of myself.

I do not have those problem addictions. Of course I am going to comparison shop for any large purchases. I am good enough about controlling spending that excess junk isn't one of my problems.

But what I do have a problem with is coming up with creative ideas for people in my life. So, for example, I would have never thought to look for https://www.zazzle.com/cup_equation_love-168099175298227864. But I'm very glad that someone out there knew enough about me to guess that this might be an item that I'd like. And my wife liked the cup a whole lot.

Does this happen often? No. But I'm perfectly happy to pay a premium for a product when an advertiser gets it right.