My workaround already was using Breeze, since it does the least modification compared to other themes available by default. Glad to see it continue in this direction.
That being said, it's expected the default icon theme does little to nothing about customizing a third party icon. When I was involved (briefly) with the KDE VDG back when 5 was about to be launched I proposed a icon style that looked completely different of what Breeze looks right now - maybe something in between of what Oxygen looks like and Breeze looks like. But Jens Reutenberg told me it couldn't go in that direction since they needed to ship certain icons "as-is", like the Firefox one, so it was better to do something that could fit anything so those "special" icons wouldn't look out of place.
Some people like to diss on flat/minimalism styles but for some situations there is a reason they look that way.
The submission title makes it a bigger deal than it is, the article clarifies that "The team reasoned that overriding another developer's branding is rude, and it also lacks the resources to maintain the icons as branding changes over time." and "Anyone who misses the old look is welcome to create a new icon theme and upload it to the KDE Store.". Nothing has really changed, especially not newsworthy.
This is KDE's decision on their Breeze theme. Distributions can ship the icon set with third party icons if they want.