"what I MUST keep long-term": tax records, MySQL databases, important documents like passports, marriage certificates, wills, land titles. (Write once, keep forever.)
"what I would like to keep long term": music, videos, photos, manuals or user-guides, memorabilia. (Also write once, keep forever.)
"what I am currently working on": system config files, programs in development, current year's tax records, travel plans, etc. (Keep only as long as necessary, a week, a month or a year)
You then recalibrate that to "what I must keep long-term plus what I am currently working on" and "what I would like to keep long-term".
On a daily basis, rsync several copies of the "what I would like to keep long term". It's possible to lose one or more copies of that, but very unlikely you'd lose all of them. These archives are currently about 6 TB.
On a daily basis make a snapshot which contains all of the 'Must keep' and the 'current work' stuff. Make several copies of that. Hold those snapshots for quite a long time. Delete older ones progressively exponentially. (You retain some very old snapshots, and more and more of the recent ones.) I try to keep my snapshots under about 12 gigs per day.
In the case of a complete disk crash, I can rebuild my 'daily driver' to where it was at the time of backup last night in under two hours. I can plug in one of my "like to keep" backups until that can get copied back across too, while I can keep running normally.
1) Remove as much data as possible: you don't have to worry about data you don't have
2) Print important documents and store in fireproof safe or bank box
3) What remains fits on a USB stick, just make a monthly copy.
TL;DR: declutter first, only then think about backups.