It’s very pleasant, but also extraordinarily infuriating, to see that things like accent colours and recoloring styles happening, after basically a decade of nope.
Very pleasant because, you know, they’re not just nice to have, they’re useful and necessary out in the real world. Adwaita’s colours look great on a good monitor but the intense white burns your retina on many mid-range monitors (and yes I know about Redshift, that’s entirely another point). And not everyone has a choice about that. Some people are on whatever laptops and monitors are issued at work. Some people just don’t have the money for another one.
Extraordinarily infuriating because 10+ years ago these things used to work out of the box (more or less – not all GTK2 theme engines supported it, but some did), and this, along with many others, were frequently mentioned in GTK3-related threads ten years ago, and responses ranged from “nobody needs that” (which sucked for us downstream, since we didn’t have the luxury of telling our users that they don’t need the thing they’d just told us they needed!) to “get out of your parents’ basement, you’re irrelevant and so are the few users you have, Gnome is the dominant Linux desktop and they’ll move to it pretty soon, too”. (I’m partially misquoting that because I really don’t have the patience to dig through my Reddit history but I think I got the insults right :-D)
Ten years of CSS hell later, it seems like GTK upstream is finally realising that:
I don’t expect we’ll see the end of the “I don’t know what XFCE is or does” era any time soon – that’s a social problem of an entire generation of developers – but it’s refreshing to see practical interests and user benefit prevailing over the curious ceremonies of the cult of Steve Jobs.
I do think that explicit support for light and dark themes would be a good compromise in the “Please don’t theme our apps” controversy. GNOME had this in a half-hearted way since GTK3, with the “force dark theme variant” in Tweaks, but like the 2019 article linked to from this one said, it could break on custom app styling.
I don’t think perfection is something required here — dark theme support on Windows and Android is actually janky as hell, but I don’t hear lots of complaints about it.
Latest versions of gnome do indeed support both light and dark themes.