In light of this, I can't help but feel the OSS alternatives to the Adobe graphics suite are pretty abysmal.

Inkscape is passable but aspects like filters are obtuse to use and that's largely because it's trying to be a good compliant SVG editor and not necessarily a good vector graphics editor.

GIMP's user experience in my opinion has been terrible for decades and every time I have given it a chance it's annoyed me into closing it. I can get things done, but it gets in my way.

As for Scribus I've never used it, but based on the previous two I'm not instilled with confidence.