I agree with you on point that it takes a lot of clicking to organize a party, and a lot of different windows side by side could be nice and practical on big 1920*1080 (16:9) or higher resolution screen, but what about 1280*960 (4:3), or worse yet smallest supported 1024*768 – how would you fit in it all there? Try it and see how it looks in window mode.
As it is now UI made to fit and look good even on smallest available resolution. And i think Devs did a darn good job of fitting it all togather.