What I see the problem with adds is that in these times, there's just no way to trust them.
Since I can't install anything on PCs I use in school, I see ads on sites I browse there (during breaks, ofc). I presume that university with thousands of students has decent security measures, but that's going kinda OP so back on track...
When you mouse over any "average" add on the internet, what you see is dozens (more like hundreds) random characters and no way to know where the add is leading to. It's the reason I don't trust ads these days, unlike in past where an add was simple JPG image and when you hovered over it you usually saw the website link. No cross-site scripts managed by third party servers and their cookies datamining to try (and fail) to guess what you might be interested in.
If ads stop to be cross-site scripts that you can't see through, and go back to static code, then I might consider not blocking them.
Safety first.