I know they haven't built these programs themselves, so it's not necessarily their fault
that these developers have gone with the everything-and-the-kitchen-sink style of UI
design. But they also chose to feature these particular projects, so someone there
thinks these are good examples, which does not speak well towards their commitment to
enabling good design.
And they aren't little things. Replacing standard buttons in some cases but not others confuses the user as to what elements are actually interactive. Not using the layouts that the operating system vendor recommends for different types of applications confuses users as to where to expect to find things. Using your own, janky set of icons without text labels confuses users as to which buttons do what.
I mean, have you even used KiCAD? It's an absolute abomination of UX.
You know how programmers have a reputation for being bad at design? You know how programmers have a reputation for "not having any common sense"? This is why.
The point is, using a silly web UI in a browser widget, as you suggested, makes the problem worse.
TBH your argument sounds like a designer trying to justify being a designer. No real users are "confused" by any of the things you've nitpicked about. You're conjuring up some uber-stupid theoretical user as a strawman. But feel free prove me wrong by finding real people on the web complaining that they're confused by those issues.
I think it's the influence of the web that has allowed these deviations from standard to flourish in a way that they couldn't have 20 years ago. When every widget on a web page is new and unknown, you just learn to deal with it. Certainly you can find bad design both on native apps and on the web.
I mean, have you even used KiCAD? It's an absolute abomination of UX.
You know how programmers have a reputation for being bad at design? You know how programmers have a reputation for "not having any common sense"? This is why.