Use of immortality in genshin is so neat to me. Cause it doesn't really exist??
One of the heavenly principles is that everything will one day be returned to the earth. For mortals this is ageing, for archons its the process of erosion. But not a single being in the world of Teyvat is truly immortal. It would've been so easy for hoyoverse to go down the traditional "divine beings are immortal, invulnerable and overpowered" route. But they didn't. The archons aren't immortal nor invulnerable and it makes them feel more human for it. They're also not overpowered either, they're obviously considerably stronger than allogenes as they've had longer to learn the ins and outs of their element.
There's no set 'level' for archon strength either, all 7 of them are at different levels to each other and experience setbacks as well as advantages depending on their environment or other varying factors (which is why power debates are stupid).
This makes the Tsaritsa's goal feel more fleshed out and more realistic. It's achievable with enough time and effort. There's so many games/shows/movies where you can tell very early on that the antagonist is pushing a rock uphill, they're fighting a losing battle, and it's refreshing to see hyv not take this route.
It's no coincidence that the Tsaritsa is the most human out of all the seven. Not just in that she apologises to her subjects, or understands what she's asking of them, but she's flawed. She's stubborn, she's a loner, she's proud and unmoving in her decision, she isn't accepting of criticism and she's narrow-minded, bordeline obsessive. She's had to harden her resolve because she was too benevolent. Ice is symbolic of all these things, and it would've been so easy to set her apart from the other archons and give her this air of superiority but they don't.
One may argue that regarding herself as the Tsaritsa of Snezhnaya is an act of superiority but I beg to differ. It's a downgrade from god, a monarchy is a man-made system, to be regarded as the Tsaritsa before the cryo archon makes her feel more human. It's an attempt at getting rid of that divine aspect of her person.
And I think, overall it's what sets apart the celestial gods from the archons on Teyvat. The archons can die, they can lose; they can experience grief, They face challenges and setbacks as they adapt with their nations, and they reap the rewards for it. They can feel achieved and proud. They're human. We as the player can relate to them, empathise with them and it gives them depth. They're nuanced and it makes the Tsaritsa's goal seem more realistic and achievable. Her motivation makes sense cause it's something we can empathise with.
The absence of these same themes for the celestial gods makes them feel less human, there's nothing to relate to. They feel empty and lacking. They're set apart both physically and emotionally from Teyvat.
Furthermore, cause I'm never done, there's humans cursed with longevity aswell. La Signora/Rosalyne, Dainsleif and Pierro. These 3 — as well as others that I haven't mentioned cause I'm not 100% sure of — act as a mental bridge for the player to relate the archons to Teyvat. Longevity isn't exclusive to divine beings which further adds to make the archons feel more human than the celestial gods.