>Gnome and GTK are designed with themes as a core feature, and have been for ages. I don't know where you heard this, but to my knowledge this hasn't been true

>Gnome and GTK are designed with themes as a core feature, and have been for ages. I don't know where you heard this, but to my knowledge this hasn't been true. GNOME 3 didn't really support "themes" proper, for a while now the only supported theme is Adwaita. It technically did support re-styling with CSS, and you could load a different CSS using the tweak tool, but this was always considered unsupported -- if you loaded a theme that had bad color contrast or makes the text otherwise unreadable or broke any number of other things that a theme could break, then that was on you. The option was appropriately hidden in the tweak tool so non-technical users wouldn't accidentally load a theme that breaks their desktop in an unrecoverable way. >Discussing what makes themes difficult to support - how to design themes that don't break good apps, and how to design apps that don't break with good themes - would be far more productive Respectfully, it wouldn't. This has already been discussed quite a bit and the problem is that if you want the full power of CSS theming then the apps will always break, because the theme can literally change anything anywhere. There is no way to design a theme or app that works correctly here, it's like trying to take a random CSS file from one website and then applying it to another random website. Sure maybe it might change some things, but most likely it won't really work because none of the class names will match up. The only way "theming" really can be done reliably is to do it in small controlled ways, e.g. I believe there is some discussion of allowing changes to the accent color similar to what Windows and Mac do.