My threat model includes a few things, but one of them is that I don't want my data available to advertisers.

GrapheneOS sort of supports that, but I found that it's nearly useless as a daily driver when set up that way. Even with Google Play Services installed in a sandbox, GPS stuff breaks, the camera is flaky, and third party apps don't work reliably. Also, the remaining built-in apps have huge gaps (no backup, no synchronized notes, etc).

Worse, I'm not convinced that sandboxing it helps privacy that much. Without it installed, the phone had multi-day battery life. With it, it dropped to whatever Google was advertising (30 hours?).

Anyway, iOS without lockdown seems to be much more secure (by my criteria) than my GrapheneOS Pixel phone was in practice. Also, I can use all the apps that are essentially mandatory around here.