This article makes me feel old, having lived through a time where you avoided using PNGs on the web because IE6 didn't support the transparency
Crazy considering how much I use the property now.
Nonsense. The only reason to avoid PNG was IE’s gamma issues: IE6 did not support progressive transparency, so at worst you had full-color gifs.
You could actually make it work with non-standard DirectX filters, but it came with its own set of drawbacks and wasn't always a viable option.
That makes absolutely no sense, because there was no other format which could do progressive transparency on IE, and short of animation palletised PNG is superior to GIF. And for non-photographic full-color, PNG is generally much better than JPEG.
So avoiding PNG just gave you larger files or worse results for no gain.
So yes, you did use PNGs in some areas (illustrations etc.), but anything that would make you think "I'd have to use PNG to do that" meant "no-go because of IE". Which generally means avoiding PNGs.
When you add gamma issues on top of that, it was pretty rare to ever use PNGs for web designs if you cared about IE6.