Baseband vulnerabilities are overhyped, imo. On proper phones (eg. pixels), their access to memory is restricted by IOMMU, ...

That just kicks the can down the road to "Why should we fully trust the IOMMU?"

Granted, it does defend against the vast majority of actors.

... because that's literally the IOMMU's job? Why should we trust the TPM or the CPU or a YubiKey or anything, really? I don't completely trust any of it but to get anything done you have to trust something at some point.