It's straightforward, but relative to whatsapp it is a huge hassle.

Imagine you lost/broken phone and bought a replacement. Whatsapp would be able to restore all your history while in Signal you are out of luck.

Apple support has occasionally asked me to reset my phone due to some iCloud issue. How do I back up my data and restore it after that without buying a second iOS iPhone?

Yes I have done it, but my wife saw me do it and said there is no way she would go through all those steps.