The thing about Apple encouraging people to move to support “Liquid Glass” is, I suspect, not that the specifics of the look and feel are cemented forever but that the API changes are something they feel they can support across platforms, kits, and time.
Here’s Apple not even being able to keep their own ducks in a row:
https://daringfireball.net/2026/03/what_to_do_about_those_menu_item_icons_in_macos_26_tahoe
What to Do About Those Menu Item Icons in MacOS 26 Tahoe

If this worked to hide *all* of these cursed little turds smeared across the menu bar items of Apple’s system apps in Tahoe, this hidden preference would be a proverbial pitcher of ice water in hell. As it stands, alas, it’s more like half a glass of tepid water.

Daring Fireball
25 years ago, when OS X was released, the platform was fragmented by support for Classic, Carbon, and the new AppKit apps. AppKit apps had Carbon menus because that was the best solution for all. (See the upcoming out-of-process menu bar) These days MacOS is in disarray and fragmented entirely due to not making strong choices. We’ve AppKit, SwiftUI, and UIKit via Catalyst. Not to mention the shart of Electron/webtech apps that are the new X-Windows lowest common denominator.
I think a lot of the work to make Liquid Glass work has been in coordinating all of these (except the web stuff) to have a consistent approach. The expression of that change isn’t great. So much work to be done on that front. But having a unified front _does_ help move the platform forward. Even if it means coming along with the worst regression to MacOS in its history.