I've found ad blockers to be more or less competent in removing the stupid European banners, but they are far from flawless. Some sites get stuck without a scroll bar for example
As for missing pictures, my argument is, either the text is referring to an image that cannot be seen in reader mode, then I'll notice and switch back to normal mode to see the image, or the image is not relevant to the text, so I just don't care for it.
This way I can see the text and pictures the way they intended it to be.
Another downside is that text content for other articles on the site that aren't part of the article, will be in the content. On the full site they'll be links or something and you just skip them with out thinking. In text to speech reader mode, it reads them off.
Images in online articles are irrelevant the overwhelming majority of the time --- 75%--95% or more. At best they're eye-candy or distractions. They occasionally provide context. Some serve as a contextual reminder. I'd suggest that information-critical graphics (there's information in the image that's not available from the article itself) are in the neighbourhood of 1% of all images. These tend to be graphs, plots, charts, or maps.
They're also generally rendered by Reader Mode, unless the site is very poorly designed.
TL;DR: This is an irrelevant concern.