This is something Apple is increasingly working on. For example, in Fall 2020 they actually revised their CPU designs (including older CPUs) with a new Secure Enclave design that uses mailboxes to more securely store the number authentication attempts inside the secure enclave.

The goal of this is to make it so that even if the FBI had an incident similar to 2016, Apple would not be able to fulfill their request to make a backdoor, and the FBI wouldn't be able to make a backdoor even if they had the power to sign and run any code they wanted on the phone.

That's how you make a secure system these days. You can't just make it secure to everyone but yourself and fight the government - you need to secure it from yourself as well.