1. Synology NAS- unlike single drive NAS- has either traditional or their own (expandable) RAID system built in. If a drive fails, it alerts you. You replace the drive and all is fine and backed up again by the RAID. While it incorporates the new drive, you can still use it, so no interruptions of service. I've been using one for 10 years and had one drive fail in 10 years. I chose to replace it with a larger drive to expand the capacity at the same time as re-securing the RAID backup. Easy. Cheap. "Just works."
2. I can't believe there is any push back to the offsite storage option such as the one I offered, as if it is some great burden. It is so easy to take a TM drive and put it somewhere other than home: safe deposit box (like me) at the bank, office desk, gym locker, family members house, school locker, friends house, etc. TM backup to another drive for a few weeks, then swap them out (regularly) at the offsite location. Cost in the offsite storage? Free to maybe $50 max.
3. Ransomware is like exploding phones, sharks biting people at the beach and crashing planes: lots of press about it when it occasionally hits but very rarely about individuals who can't pay substantial ransoms, almost always corporations or government-level players where the ransom can be interesting. Nevertheless, if one executes #2, that backup option is detached from the internet, so there is no way hackers can penetrate the impenetrable wall of disconnected storage. Worse, worse case: one retrieves their data from the #2 backup. Realty case: individuals will very rarely- if ever- encounter ransomware (or plane crash, shark bite or exploding phone) in their lifetime... unless they do dumb things like downloading questionable stuff from questionable places to up their risk of viruses, trojans, etc.
4. Ease of use for the winner. No question at all that iCloud is easier to use than running your own Cloud with something like Synology. However, 12TB of that ease of use will cost about 2 iPhones and a pretty good Mac over just a few years... with a continuing expectation to keep paying in more iDevice + Mac equivalents forever. In over-simplified terms: one is paying a LOT to forever rent a hard drive "in the sky." 12TB of cloud storage in your own Synology costs about $100... ONE TIME vs. $60/month for up to forever.
Do the math. $100 for 12TB of your own cloud for upwards of about 10 years vs. $7,200 for 12TB in the sky over the same time span. What could you do with the extra $7,100? That's the point in all of this. It is not "I hate iCloud," it is "I don't like iCloud high pricing. How can I get the bulk of the benefits for less?" 12TB of storage is 12TB of storage. Your data or your friends will never know- or care- if your cloud is branded Apple or not.
Anyone good with spending several thousand more for iCloud, good for you: there are certainly tangible benefits to iCloud, especially since it is deeply integrated into all Apple operating systems. Those who might rather save those thousands and/or create spare cash to buy their next iDevices and Mac, rolling your own cloud can deliver the bulk of the benefits at far less cost. Choose what best fits you and your budget.