> We’ve removed all of the colorful 3rd-party app icons from the Breeze icon theme. This was a complicated decision, but ultimately we reasoned that overriding 3rd-party app developers’ branding was rude, and we also realized that even if we didn’t care about that, we lacked the interest and resources to maintain the icons as those developers changed their apps’ branding over time. Anyone who feels sad about this is welcome to create an icon theme containing only the old colorful 3rd-party app icons which inherits Breeze, and stick it up on https://store.kde.org for others to use. (Nate Graham, link)

Honestly I'm fine with that decision. Personally I'm using the Papirus icon theme and the kde store - completely free AFAIK - is a good option for this kind of customization.