Just posted this feedback regarding macOS 26 "Tahoe" (FB19853155) - please support with additional submissions if you share my view. I will miss the beautiful and individual designed icons of the past!
"macOS 26 is enforcing squicles for app icons, falling back to a grey background for 3rd party apps without a compliant AppIcon asset.
As a result many original app icons are reduced in size and hard to distinguish because they share the same background color. Although I respect Apple's strive for an iOS-like UI on Macs, a smooth transition path would be more user- and developer-friendly ... e.g. with some info.plist property to opt-out icon migration, potentially ignored by a future macOS version.
The current solution causes a bad usability, and makes the system look inconsistent as many - especially free - software will not be updated with new icon designs. Please reconsider this bad design decision!"