I'm running both Confluence 5.8 (reached EoL) and a cloud version. I just wanted to reach out to Confluence team and express my big frustration because in my opinion the new blue interface looks unprofessional and inspired by some ms win10 user. New set of icons like this is 
also looks crappy as a tablet modern.
I just wanted to ask Confluence support what is the last version with the interface I like, but according to https://www.atlassian.com/blog?p=37521 no dedicated support now.
I must repeat, very frustrating. Don't break what's not broken.