Example: https://www.oreilly.com/openbook/motif/vol6a/Vol6a_html/V6a....
Very sharp-edged 3D boxy window design creates heavy cumbersome feel.
Inconsistent pixelly fonts.
Oddly aligned text in button.
Diamonds happen to be a shape that maximizes pixelation.
Indent in vs. out is cognitive heavy to process, relative to something less pure-dual.
Black selection border doesn't have consistent widths.
Separation line between big button and little buttons, despite obvious size and shape differences that already make that distinction.
Extra little borders defining window box corners from horizontal and vertical borders - a distinction that surely didn't need highlighting.
No rounding. (Granted, rounding would look pixelated.)
TLDR; It looks like an industrial lead brick you really don't want to drop onto your foot.
This actually designates an area where you can click and drag to resize the window. I'd argue that this behavior has become a ubiquitous expectation because of this design.
Like, a 1px border isn't too back when I have a keyboard shortcut that makes a full 1/9th or so of the window's area the effective border. But when it's exactly a pixel — and combined with macOS's cursor's hotspot not being on the cursor tip … it just takes what should be simple to way harder than it need be.
And then there are the too skinny to grab scroll thumbs, which are also invisible without gratuitous scrolling. And they disappear quite quickly.
Three alternate solutions:
1) Long hover (1/4 sec?) near window edge, to make edge grabbier. Long hover (1/4 sec?) near scrolling side for scroll bar to appear.
2) Pressing one of the modifier keys to make edges and scroll bars appear and be grabbable.
3) Toggle keyboard command, that makes edges slightly thicker and holds scroll thumbs visible, vs. hiding them.
This is because the screenshot is apparently rasterized from data for print version (".eps.png") at a resolution that does not match the resolution of the two bitmap images in it.
https://news.ycombinator.com/item?id=25734498
https://medium.com/@donhopkins/the-x-windows-disaster-128d39...
SGI had their own version of Motif with a look that was more like Mac and Windows of the time.