My experience is the opposite - FOSS is often obtuse, with an assumption that you see things the same was as the dev, which is usually a single person or at most a very small group. Add to that, documentation is nominal, or non-existent, and quite often lacking even a high-level description of what an app does, let alone where to find features in an app. FOSS devs often don't even follow menu layout that's been pretty well established at this point. For example, I've found the Settings menu under File, Help, Tools, View, etc, in different apps.
Proprietary apps are usually developed by a team, one that's studied the market segment (or another group has), and usually understands how that segment operates. They then develop the app based on design goals established by a team other than the developers, with UAT (user acceptance testing) performed at given stages (this is even more frequent today with Agile project management). It's not uncommon for a UI to be mocked up and given to end users to validate UI design/layout choices long before anything is even developed.
These devs usually follow a company standard process, with code reviews by other people. Their changes must be approved by management, and those changes are often requested and reviewed by other teams before being submitted to the dev team.
Most FOSS simply doesn't have the time or staffing to do what most proprietary software dev does.
And I use both proprietary and FOSS all day long.