I have never had an issue with an iCloud backup. I think I’ve done about 6 or 7 restores from iCloud. The last two time I bought a new phone, I used the new Quick Start direct device transfer method, but I had an issue with my last device (13 Pro) that required a factory reset and restore, which I did from iCloud, and before that I restored all of my new iPhones and iPads from an iCloud backup.
I will say that I will do a computer backup before I do the factory reset (if I can) as a “just in case”, but I have never needed it.