Remember there was a time, a sweetspot, when browsing was something that would never tax any modern computer?
Nowadays, with my work issued laptop, many web pages (especially apps) load slow or are laggy. They even continue to load stuff while I scroll, which makes everything worse.
And we got used to that, just because each week a new tool, tracker or framework comes out that just needs to be out on the page post haste.
The stuff that web developers get away with through the ages would have gotten other devs fired.
Look at how crisp and usable the Win2k UI was, while web pages looked like that.
Web devs today are the same people who put font gifs, colorful backgrounds, flash intros and midi files on websites back then.
There was an underlying issue that web design was difficult before browsers supported CSS 2.1 well. You really couldn't get HTML elements to fit a graphical design reliably. CSS 1 didn't really have the ability and table layouts were pretty coarse. Using raster graphics was pretty much the only way to get fancy designs to look right across browsers.