I almost couldn't go on reading when I saw that. Definitely had to cringe. Look, this company makes reasonably decent tools for the enterprise but I seriously don't get how they justify what they call UI design.
The design principles are an ideal that we're striving for, and while we're proud of the improvements that we've made over the last few years (seriously, look at JIRA 7 vs JIRA 4, 5, or 6) we're always looking for ways that we can do better. JIRA as a product pre-dates not only our design principles but also our first hire of a designer by a few years :) It's one of the most flexible tools in the industry and that (currently) comes with some attached complexity tax. We're continually making improvements to highlight happy paths, simplify onboarding, and even remove some obsolete or under-utilized features, to pare back that complexity. However it takes time and many iterations to get that right. Particularly, when you have to balance simplicity with the "power features" and flexibilty that many customers count on us for. If you have feedback on rough edges or clunkiness that affect you I'd love to hear it! My contact info is on my profile.
If you'd like to read a bit more about Design @ Atlassian, our team posts pretty regularly over at on Medium. This one's a good read if you have a design bent: https://medium.com/designing-atlassian/product-to-platform-e...