The CSAM scanning system Apple describes prevents[0] the sort of abuse that has historically been used as as argument against convenient strong encryption. By casting a very specific net for the most egregious abuse, they defuse the strongest political argument against E2EE while remaining compatible with a strong E2EE system. Read the docs upthread - they go to lengths to cryptographically enforce the topline privacy guarantees. Client side scanning of iCloud-destined photos is a net-zero change, since they’re already doing this server side. Scanning plus future E2EE is a strict improvement in privacy for iCloud users.

If you're concerned about ways Apple might access on-device contents in the future ... there's myriad ways for your OS vendor to circumvent the privacy protections offered by your OS ...

[0] or is at least as comprehensive a mitigation as possible on systems with access to cleartext