@rumba

UI without art is just a bunch of shitty buttons no one wants to press.

You're describing Usability. This is, in fact, its own discipline that should direct both UX and UI.

Disagree. I do not believe that the design of a button is art. Even things like the roundness of the corners have justifications that relate to usability, which is an inherent part of design, and it always has been. Visual hierarchy is usability. Type selection is usability. Gestalt theory is usability. The hanging punctuation in medieval manuscripts is usability. UI, UX, usability: It's all just design. In fact, if you're a "designer" who is regularly putting out work that doesn't meaningfully consider usability, you may well be an artist instead!

That's just saying it's a lack of talent because FOSS teams are inhospitable. Blanket statements like that ring as a stereotype.

This is a thought-terminating cliché, but thanks for demonstrating my point by flatly negating my personal experience as a designer who does volunteer for FLOSS projects from time to time.

The consumers of the product know nothing about basic design principles either. Does their opinion not matter either?

This is a strawman. My point was not that no one's opinion but that of a designer matters. My point was that when designers are making recommendations based on their knowledge and experience that relate to design problems, the opinions of people who do not have expertise on these matters should not be treated with equal weight.

So, forgive me if I'm reading too much between the lines, but what you're saying here is if FLOSS wants better UI, they need to engage someone who says they're an accomplished UI artist and blindly execute their vision even against their own impressions of the requested work?

Yea, again, this is not what I'm saying. If a designer says "hey, we should probably put that button here for X and Y reasons," devs should have the humility to understand that, as a design professional, they probably have a reason for saying so that goes beyond 'I think it looks nicer.' That's the cultural component. The technical component is that FLOSS projects need to meet designers where they are and not ask them to use platforms they're likely not familiar with in order to participate.