I'm sorry, but I still don't get it. Mavericks supports iCloud, but *not* iCloud Drive, which is the facility that arrived with IOS8 and Yosemite. However you depended on iCloud before you bough the iPhone 6, it still works in Mavericks.
I'm sure that quite a few people went for iCloud Drive on their IOS8 devices, not realising that there would be this gap in support on Mavericks. It seemed to me that Apple was very clear about that (but I was involved in the seed builds of Yosemite and iOS8 for quite a while, and that might be distorting my view).
You're obviously correct that it was a mistake to for you upgrade to Yosemite. I don't want to rubn salt in the worund, but there are two other major points here for the future.:
1. You should *never* upgrade without a backup. You should *not* be running a server without a backup. If you don't like/want Time Machine, use something like Carbon Copy Cloner to make a one-time backup. It's free for (I think) 30 days and very cheap anyway.
2. Separate your server operation from your other operations. iCloud Drive and other new iCloud facilities on the iPhone aren't related to Server. I'm aware that there are Profile Manager capabilities that are designed for IOS8, but they're available in Server 3.2.2 (which, it must be said, has issues of its own).
The sum of this is that I go back to by previous post - you've adopted an approach which entails buying Server 4, and missed the chance to avoid it by having an available backup.
I can completely understand why you're annoyed and frustrated - I've made similar mistakes myself, many times - but I really think that projecting your anger on Apple is wrong.