There are still such tools, you don't have to use the past tense here.
Total flashbacks to windows 95 and every so often changing the windows color, text font etc. for the entire system
Good times
Multiple hamburger menus with a scattering of cryptic icons stuck at arbitrary places on the screen. What does the swirly icon with up arrow do? No text label for you!
Oh and let's move the next button to the top left of the screen and not highlight it. Mmmm that's some good UI design.
Have you considered that the average user never cared and never will?
Having ultra consistent styling across all apps ruins the ability to... you know... sell the software. It gives far too much power to some group of annoying elitist nerds in denial of their opinions preaching UI/UX pseudoscience.
> But hey, we can write same code to work on windows, mac and mobile ! It will work shit in all of them and be slow but we don't care!
Ain't nobody got time for reading even shittier documentation for badly written OS APIs.
This has more to do with the current state of GUI frameworks than with developer mindset. Microsoft is between GUI frameworks and rumoured to have deprecated everything between win32 and WPF, and in the meantime they are pushing React Native. Apple doesn't seem to know what to do with desktop environments and is stuck between their legacy objective C frameworks which they seem to purposely hide any form of documentation and swift-based frameworks which are broken out of the box. Linux has a couple of options which are ugly as sin since ever. There's Qt, but their licensing scares away anyone with two brain cells to rub together.
So where are we left?
Well, with webview-based frameworks, which is the worst of both worlds but at least they don't look half bad.
Except that webview-based frameworks are a far lower-level abstraction than any native widget-based framework. Developers are forced to reinvent the wheel, and this means dropping any standard look-and-feel because that's already ugly to start with but takes even more work to get into a working state.
And all you want to do is to provide a GUI for users to click around.
Even in Linux there were tools to sync gnome with QT look so you could have one theme applied to every app for nice and consistent look, all the way to how the common icons look.
Nowadays ? Every fucking app gotta have their own different styling. Will the setting icon be three dots, gear, or honey badger ? WHO FUCKING KNOWS. You'd be lucky if you even get a choice between light and dark theme
But hey, we can write same code to work on windows, mac and mobile ! It will work shit in all of them and be slow but we don't care!