And just as trustworthy as devices that are equivalent to desktop Hardware with UEFI, IntelME, etc.

So you mean like.....99% of all hardware in the world? Lol

If you're that hardcore into privacy or your threat model justifies it, then grapheneos isn't for you because you're already well prepared to make significant compromise and/or expense to pursue that goal.

GrapheneOS is more about leveling up more common people's privacy

Don't let perfection be the enemy of good

Look, I love FOSS and open platforms, to the point that I will only run proprietary software if it is sufficiently sandboxed AND there is no alternative. Unfortunately, hardware just isn't there right now. You basically cannot have a modern computing experience on fully open hardware. At some point you have to make a compromise with it, it's unfortunate but it's the world we live in. Typically that compromise is either all open software with closed hardware and firmware, or all open software and firmware, with incredibly old or restricted hardware (which is still closed). I have yet to see any solution that involves truly, fully open hardware and so you basically have to just draw an arbitrary line and say "this is good enough."