It's tempting to make these sorts of claims because a mild level of user hostility plagues most FOSS gui apps that we encounter, but I think it's more useful to think instead of how difficult it apparently is for organizations to make effective UX design decisions.

It's equally likely that a "horrifyingly designed UI" (much like Eclipse) came out of an Enterprise Software shop.

None of the incentives are aligned toward optimizing user experience (i.e. rarely do the people who use the software the most have any say in how it gets built). And, because the way responsibilities are divided (i.e. one team per set of functionality, I imagine), no one in the leadership structure is empowered to make big changes that affect everyone; and so you're left with small incremental improvements and shitty error messages.