I was considering icloud as a partial replacement/extension for my 365 onedrive account. Eventually I found onedrive since the last updates easier to manage as a synced cloud based backup repository for a big chunk of my data (800Gb+). If I use icloud drive to automatically sync all of my files, it breaks most of my windows laptops, and my mbpro is constantly busy with managing diskspace. After playing around with icloud drive I have disabled it on all my laptops, and I only use the webinterface to push/pull files whenever I need them somewhere. It is a bit silly but it seems to be the only way it can be used sensibly with more data (4K holiday clips are a big impact on the cloud storage).
For my active documents and files I am back to onedrive, which actually works better on my ipad and iphone as well.
I do use the icloud account to do full backups of my apple devices.
For 10 euro a month across 6 family sharing accounts and 12 apple devices I think it is worth it to keep the extra backup which is easier to recover.
It is a shame icloud could have been so much better than the others if they had thought it through better. At the moment I feel Microsoft is best positioned in the cloud storage/backup space, especially considering the price/performance/features ratios.