However loading the images early wastes bandwidth, and it hurts SEO. In my case the user can live without those images, so it's a sacrifice I'm willing to make. I hope that descriptive alt tags will help.
On the other hand, the whole text is there from the start and every other way is wrong.
This is one of the big problems with the modern web, It puts you in this doom loop: sacrifice the user to please Google to get users.
In this case it means preserving bandwidth unless it's needed. I lazyload images for the same reason I serve 4 different image sizes.
You can have a slow, bloated website but great metrics, because you’re doing the “right” things.
However lazy loading images that are not on screen is generally a good thing. Images are typically the heaviest part of a website and loading them only when needed is good.
The article in question acknowledges that, but is criticizing the implementation and failure mode.
I haven't seen any statistical evidence, but from my personal experience a typical website with some images, some JS is often heavier on the image side. Fonts can be large too. PNG are heavy. Videos are the heaviest but rare.
However per byte impact on performance (which is a very vague quality) is very different. Often JS degrades performance more than images.
No. An article should always be loaded in full. I clicked a link to a document, that means i wish to view it. Not half, not the first page, the whole thing. If you have tons of content in a single document, you should probably paginate anyway. Images are usually few, and if not totally unoptimized (which you should do before lazy loading), not a huge drain. By all means, lazy load all the unimportant banners, ads and UI elements. Better still, don't add them at all. Only for infinite scroll would lazy loading make sense, and even then batched by 10-20 ahead (or more), so I don't spend time waiting half a second for each and every image.
The heaviest part is nearly always ads and analytics. Cut those down first.
MDN says img lazy doesn't work unless javascript is enabled, so easy peasy to use javascript to make the images unlazy after onload.