I suspect that the difference in quality & simplicity between OpenBSD & Linux is less a matter of license than historical accident. Given two identical projects with identical contributor profiles, differing only in license, I don’t expect that you’d see any difference in quality.
However, in the real world I think that the GNU world has long had a tendency to add feature upon feature (which is nice) and to treat each subproject in isolation (which is less nice) which can lead to fragmentation across the GNU Project as a whole (which is very much Not Nice). While Linux is of course not part of the GNU Project, it is the kernel of a GNU system, and the Linux kernel on its own is not terribly useful.
Meanwhile, the BSDs have always been integrated systems. There’s not reason inherent in the license that they are — they just are, and since they are they continue to be.
However, in the real world I think that the GNU world has long had a tendency to add feature upon feature (which is nice) and to treat each subproject in isolation (which is less nice) which can lead to fragmentation across the GNU Project as a whole (which is very much Not Nice). While Linux is of course not part of the GNU Project, it is the kernel of a GNU system, and the Linux kernel on its own is not terribly useful.
Meanwhile, the BSDs have always been integrated systems. There’s not reason inherent in the license that they are — they just are, and since they are they continue to be.