The thing is, trusted computing as a security feature isn't useless. For the particular case of phones, people generally use relatively low entropy passwords, because it's impractical to do otherwise. The Titan chip uses trusted computing technologies to ensure that an attacker with physical access cannot bruteforce the password, which it does by forcing a timeout between successive attempts. It might do other things too, this isn't my area of expertise, but (I believe) it isn't needed for the general functioning of the device, as opposed to e.g. the intel ME.

Of course, a security chip that you have the power to control would be better, and no less secure, but that doesn't exist. However, neither the OS itself not the apps directly depend on trusted computing. Otherwise GrapheneOS couldn't exist in the first place.

Note that this problem doesn't exist on desktops or laptops: it is entirely possible to memorize a passphrase around 96 bits of entropy, which is high enough that it can't practically be bruteforced, especially if the algorithm to check if it is correct is computationally slow.

So, you lost a bit of sovereignty for your phone in the interest of security, but phones aren't private to begin with: the actual modem also uses trusted computing. The devs behind GrapheneOS considered this the best solution to the problem, after weighing the pros and cons. Personally, I'd be happy to have a flip phone which has no password, and then do everything of significance (possibly including call and SMS) on my laptop. That is to say, I'd rather I didn't have to use GrapheneOS, but it's compromises align well with my own for now.

Trusted computing and TPMs aren't inherently bad. Like all issues of trust, it comes down to who the trusted parties are and what they're asking of you.

So for example, let's start with the idea of a work computer. Say you work for a bank and they issue you a laptop. In order to access all the sensitive data related to a bank, certain guarantees must be made about the environment. The hard drive must have full disk encryption (FDE) so that if it's ever lost or stolen, the information that may have been on it can't be compromised. This is not your laptop. This is not your environment. This is for the most part, totally fair.

Now let's consider Microsoft and your personal device. Microsoft is forcing you into their trusted environment by requiring online accounts and TPM/SecureBoot. And how do you benefit? FDE through BitLocker, sure. But you know there are other FDE solutions and BitLocker results in you losing control of your keys because they are automatically uploaded through your online account to Microsoft for "recovery" purposes. ~Source ~Related What Microsoft is really saying here is that they have a trusted environment, and if you are to be a trusted party in that environment with the "privilege" of accessing their software and services, you must submit your personal device to their rules. Are you starting to feel the icky vibes here?

This is made worse by TPM 2.0 supporting remote attestation.

This of course raises the question, verified to what degree and to whose standards? Are they simply trying to protect us from maliciously crafted software, or is it DRM to prevent running pirated content, Trusted Platform Module (TPM) 2.0 and Secure Boot for Call of Duty. Of course this is ostensibly for anti-cheat, but you see how quickly that moves adjacent to other purposes. How much are you willing to give up to maintain (a sense of) security?

EDIT: One final point. Trusted systems are the general security engineering concept of protecting systems through enforced policies to achieve certain levels of trust. Trusted Computing is a very specific set of technologies with a board of directors worth taking a quick look at ...