So we I had two things happen in quick succession that made me also turn to online backup:
1) we had a plumbing related flood at our house in the middle of the night and my NAS was ALMOST ruined! I felt safe because we had a NAS (two mirrored drives). we were about 1 cm away from having our NAS ruined, and that would have been 7 years worth of photos LOST.
So hubby and I both started moving all the photos from our NAS to google photos so they would be online somewhere (most of them were older photos from a cell phone or our very first digital camera years ago).
And THEN 2) the HD on my main computer died. Totally unexpected, only a few years old. And I hadn't yet backed up the most recent 1 yr of photos to my backup NAS because I was still editing them and working with them.
So now we use backblaze to automatically back up all drives! super easy and cheap.
I still upload edited photos to google photos for many reasons:
1) it's a great way to share photos with family (my hubby and kids and I all add photos to shared folders!)
2) many services now can connect direct to google photos (I was making a photo video project for my son using adobe spark and it let me connect to my google account!)
anyhow, DEFINITELY back up!!