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brent Theme problems with Gnome 43, on the one hand, and Nautilis and other apps, on the other, have been reported on the web recently.
As Staudley explained, "The GNOME project keeps moving more and more apps to libadwaita theming, the latest being, among others, the file manager Nautilus. This means that it no longer respects the system GTK widget theme (as set in e.g. Budgie Desktop Settings), and also might not adjust to dark themes correctly."
While the problem surfaces in Solus DE's that are Gnome-based, as reported in this thread, the problems do not appear to be confined to Solus. That doesn't surprise me. Upstream/downstream problems are common in Linux, and take a while to resolve, given the large number of interlocking pieces and the lack of coordination between the developers of the various pieces.
It is almost inevitable that when a major upstream component changes, problems will need to ironed out downstream. No magic wand.