The Firefox/Thunderbird example is absolutely ridiculous - it's not up to these application developers to decide what icon or colour the user sees. It's up to them to provide defaults. As you say, it's clearly still Firefox - but even if it weren't, there are several good reasons I can think of that a distribution might want to change it.
What bugs me is the attitude that the solution is to reduce the usage of themes, as opposed to improve the theme engines and app dev toolkits. Why shouldn't the OS be able to impose a global stylesheet for colours, images used for semantic icons, sizes of common elements? If I, as a user, want to starting fiddling with my system theme, is it not likely that I might want all the apps on the system to play ball? Sounds pretty jarring to me to have one or two apps with their stubborn hardcoded "branding". (Oh wait, that's what we already have with Electron apps that don't respect the OS theme or conventions, and they suck!).
Oh, apps can't be restyled without manual work they say. "Until this perception changes..." they say. NO!
In an ideal world, applications could be built easily in such a way that allowed them to be themed without causing major UI bugs. The fact that this is such a large issue with GTK apps is surely further evidence that GTK has a bit of a problem - especially considering that other UI platforms are able to do a better job.
Perhaps - and I'm really pushing it here (/s) - solving the root causes of issues arising from custom themes relating to sizing and spacing might actually have other benefits as well. Like better support for UI scaling. Maybe the scope of themes needs to be reduced a little so it's easier for application developers to support?
The Firefox/Thunderbird example is absolutely ridiculous - it's not up to these application developers to decide what icon or colour the user sees. It's up to them to provide defaults. As you say, it's clearly still Firefox - but even if it weren't, there are several good reasons I can think of that a distribution might want to change it.
What bugs me is the attitude that the solution is to reduce the usage of themes, as opposed to improve the theme engines and app dev toolkits. Why shouldn't the OS be able to impose a global stylesheet for colours, images used for semantic icons, sizes of common elements? If I, as a user, want to starting fiddling with my system theme, is it not likely that I might want all the apps on the system to play ball? Sounds pretty jarring to me to have one or two apps with their stubborn hardcoded "branding". (Oh wait, that's what we already have with Electron apps that don't respect the OS theme or conventions, and they suck!).
Oh, apps can't be restyled without manual work they say. "Until this perception changes..." they say. NO!
In an ideal world, applications could be built easily in such a way that allowed them to be themed without causing major UI bugs. The fact that this is such a large issue with GTK apps is surely further evidence that GTK has a bit of a problem - especially considering that other UI platforms are able to do a better job.
Perhaps - and I'm really pushing it here (/s) - solving the root causes of issues arising from custom themes relating to sizing and spacing might actually have other benefits as well. Like better support for UI scaling. Maybe the scope of themes needs to be reduced a little so it's easier for application developers to support?