I have found myself needing to upgrade to the largest iCloud storage space to hold my Photos library, and now have plenty of space. Apparently I cannot mirror my iTunes music library on the plan I have, and now it appears that I cannot use Time Machine natively with it either which would be nice as I do not use my Time Capsule at the moment. I simply do not understand why Apple has not made this a business case for their large iCloud plan.
I've decided I'd like a Time Machine backup on iCloud and work reasonably well. I do not need the "restore on blank hardware" functionalty, just an hourly backup. Just putting a sparse image on iCloud and telling Time Machine to use that, will most likely result in a copy locally which I do not have room for on my local drive.
Is there a way that I can use iCloud for Time Machine in a reasonable way so my lone Macbook gets backed up like with Time Capsule?
iCloud is not a backup solution, it is a sync solution.
It will hold phone/pad backups, but not computer.
You cannot use it to store data that is not also present on your devices, other than such as offloading full-resolution photos or documents in low-space situations locally.
For true off-site backup you need to be looking at such as Backblaze.