A lot of things designed by software engineers, including a lot of F/OSS, is objectively bad for usability. That’s not hyperbole, there are things you can objectively measure (Fitts’ Law, number of operations to complete common tasks) as well as more subjective things (such as discoverability of features, visual cues for interactivity, and so on).
Unfortunately, a lot of interfaces designed by designers in the last 15-20 years are the same.
I think the cutoff point was when people started talking about UX instead of HCI. Human Computer Interaction is a science that incorporates cognitive and behavioural psychology and is driven by user studies to actually measure their claims. User eXperience is a buzzword, mostly pushed by people who didn’t want to go to the effort of studying usability to justify why people should adopt their bad ideas. There was a period of about five years where no one who actually knew what they were talking about said UX, which made it a useful filter, but now even good designers use the term.
‘Software engineer’ may mean someone who analyses requirements, designs maintainable and scalable systems, and produces high-quality code. It may also be someone who can write code that kind-of works if you don’t look too carefully.
Similarly, ‘designer’ might mean someone with a strong background in psychology, who will carefully examine user stories and build a system that gets out of the user’s way and behaves in a way that is a joy to use, or it might mean a failed artist who wants to get their ‘vision’ into a real product.
Unfortunately, the latter seems to be dominating the profession. The Design Museum in London used to be my favourite museum because everything in it was form following function. Things that were aesthetically pleasing but also worked perfectly for their intended purpose with minimal user friction. One of my favourite bits was an exhibit on the evolution of the Tube map, as the realisation that users needed to know the location of stations but not of the lines between them gradually dominated. The last time I went, it was entirely things that matched the private aesthetic of some ‘designer’ and were barely usable, including an entire floor on some of the least comfortable shoes ever made. And that’s what the profession is lauding. It was incredibly disappointing.