Can you give us one example of a stellar open source UI you use daily?
Blender is one of the 2 or 3 dominant tools in its field. It's a niche field, so it's not for office work, but is nevertheless an incredible tool by any standard.
For almost anyone's purposes, LibreOffice is better than any closed source equivalent tool (though some of them do have specific features that are critical for some users). The only issues with it come from being forced to interoperate with data generated by closed source applications. I don't happen to enjoy using LibreOffice very much, but there's denying its "stellar" quality compared to the alternatives.
[ EDIT: I really can't fail to mention VCV Rack, a libre+gratis virtual modular synthesizer. It wasn't the first such tool, but it is by far the most successful, and by far the best, at least in terms of user experience. It has also created an ecosystem of module developers (more than 2200 modules already), which is both a reason why and an indication of just how stellar a tool it really is ]
Of course, as a software developer, I could name a long list of FLOSS tools that are also stellar, but you and others would likely dismiss them as not of interest to "the general public". In the context of this article, that would probably be fair.
But I don't think it's surprising that highly complex UI-driven applications aren't as plentiful in open source, where the sweet spot (from my perspective) has been smaller applications that scratch particular itches. Would an open suite of office tools even get off the ground today, built from scratch without funding from Sun and then Oracle?
Maybe I was just burned too hard by trying to figure out GIMP.
The same can be said about MS Word, which has become much worse than LibreOffice, also since many years.
I have been using MS Word for 30 years, but recent versions frequently surprise me because when I have to search some command through its menus it never is where I would expect it.
With older versions of MS Word, I had no need for a manual or for a help command, because I could easily discover how to do anything that I had not done before.
With the newer versions of MS Word it is hard for me to discover how to do anything that I have done many times before, but not recently enough.
Even if I have used LibreOffice for much fewer years than MS Word, with it, like with the old MS Word versions, I never had difficulties to discover how to do something.
These days, I will never use willingly MS Windows Explorer or MS Word, instead of their open-source equivalents.
These are just some of the most obvious examples of commercial programs with a bad user interface, but there are many more.
Today, the world runs on open source, so we shouldn't call it "clunky".
