GTK uses Pango/Harfbuzz and some other components to draw text, all of which are widely used in other Linux GUI stacks. GTK/GDK do not draw text themselves, so your complaints are not with them directly.
I'm not asseting that text is being rendered incorrectly. I'm asserting that after rendering, the text is being downsampled.
I'm not asseting that text is being rendered incorrectly. I'm asserting that after rendering, the text is being downsampled.