It depend on your phone usage.
For me the phone is an accessory with nearly everything on it a copy of what is on my laptop. Anything I want to keep long term, like some photos, I transfer to my laptop as soon as I can. Usually the same hour if not the same day. Everything else on the phone is easily reinstalled from the Apple Store (apps) or from my laptop (music, keepass data, etc.)
(Edit because autocorrect keeps wanting to change “keepass” to keeps.)
I probably don’t need a backup of my phone at all but it does make it convenient if I need to send the phone out for repair. In those cases I just factory reset the phone before handing it over for repair then restore it when I get it back.
If your phone is your primary device and there are things on it that you can’t afford to lose then your situation is different.
Cost might be an issue but setting up a NAS should not be a barrier. I haven’t worked with all brands and models but I have set up several over the years and most are very straight forward.