KDE has always been the most customizable DE in Linux. Complaining about the default looks of the next version of KDE makes absolutely no sense to me because you'll be able to change it. The transition to KDE 5 (kdelibs + plasma + applications) is about so much more than a new theme, as I'm sure most people in this thread are aware of.
But just in case you aren't, and haven't bothered to read anything about it, here's the quick and dirty:
1) kdelibs is becoming more modular. What this boils down to is that building an application on kdelibs 5 will pull in less kde libraries, thus the resulting application will be slimmer.
2) Wayland support, both in plasma and applications compiled against kdelibs (although it's not completely done yet, the framework is there).
3) Making use of qt5 (which is also where a lot of wayland support comes from), specifically rewritting things in Qt QML. This makes kde applications more consistent and easier to write and maintain.
Sure, they are making a new default theme that is more in line with what is popular today. Although it seems that most of what is heard about Oxygen is negative things, so it's no surprise they are changing it. But you will be able to change the theme to your hearts content, if not immediately upon release, soon enough. To imply that KDE plasma 5 is a step backwards because of it's default theme is not only niave, but hurtful to the project as it gives people who are unaware of what KDE 5 is all about the wrong impression.
Anyways, that's the end of my rant, as I believe I not only got my point across, but also clarified the situation for anyone who is simply reading this thread without bothering to read any other information about KDE 5.