What's disappointing is that Apple has zero accountability for any of these services. Nobody would be so critical of iCloud if it wasn't your only sync option on iPhone, but they force everything to go through them. Apple says 'trust us ;)' and gives the user no way to confirm that they're not decrypting your data as soon as it hits their servers.
The argument is the same as it's ever been. Apple took away too much of the user's control; if the iPhone were a more open platform, nobody would be squabbling over our only sync option.
Edit: Background Sync has apparently been available as an API since iOS 13, but that doesn't change Apple's lack of accountability wrt security practices.