Thanks for voting!
One alternative is to subscribe to iCloud calendar with your Exchange/O365 email accounts or any Outlook account, and then sync the same accounts in Outlook for Mac. See details:
An error occurred while saving the commentJenny commented
Im the only one thats working on a MAC in the office, because I do graphic stuff. Its so annoying I cant synch the iCloud Calendar, which we are all working with in my Outlook. I also cant use the workaround, cause the Mail im using is from the host 1&1 which is only supporting IMAP. Aaaaand I cant add two IMAP accounts with the same address in Outlook.
Cant believe such a simple feature hasnt been implemented yet!