[dwaite]

Writing good UI/UX and having your software have a vibrant set of open source contributors are usually opposing goals, similar to how you don't see a lot of microservice devops architectures sold as on-prem products. It's certainly possible, but it has to be a fundamental decision and makes a lot of things harder.

Someone might contribute a nice screen layout, but actual design of a user experience involves design, which is usually a process of intelligently deciding on limitations.

Slack and iTunes often get smacked around for their designs because they are kitchen sinks of features, which makes them bulky and non-intuitive.

Open Source communities tend toward this sort of kitchen sink by default. This is because people are contributing the features they want and need, not the ones which fit into your product plan. So you typically see the most success for software that is under an open source license but has limited or banned the ability for people to contribute.