Nothing wrong with an unobtrusive, not tracking, banner on a side of a page. Related to what the page is about.
That's an even more evil ad than the obnoxious and irrelevant variety because something related to my interests has a higher chance of successfully manipulating me.
It's a distraction from the content that I actually want to see and I should not have to spend the bandwidth on loading it or the battery on rendering it.
While that would be miles better, there's still plenty wrong with it. Most advertising is designed to trick people into either buying something that they don't need at all (e.g. consuming more soda instead of drinking water, or getting some gadget, or more clothes than they need), or into buying the an objectively worse option (e.g. buying a more expensive fridge that will actually last less time). This is the goal of B2C advertising: tricking people to behave less rationally in their consumption behavior.
The only way to avoid this is to just block ads - even unobtrusive content-relevant ads. You may think ads can't trick you, but that has been shown time and time again to be false.