What makes ads a blight on websites is rather simple when you look at the scheme of things. I understand websites are reliant on monetary factors to keep running such as server costs etc. However, the caveat is balance. A user shouldn’t be inundated by huge amounts of ads. Some of the sites I go to you have pop up windows that show up randomly in the middle of an article as you’re reading, and hard to close without clicking on the ad. Kind of reminds me of back in the day when you would go to a page and the content was overshadowed by those glaring ads that would draw you to them away from the content you were Looking for. As a designer you should not have more ads than you do content. For example, when I left Reddit I was seeing ads on my feed at a rate of almost 1 ad for every 2 posts. That’s overkill. You only need 1 ad every 7 - 10 posts