The Lands Between are doomed no matter which ending you pick
Let's go over the obvious ones, if you pick The Age of Frenzy you're willingly destroying the world, so nothing to explain here, really. If you pick The Age of Dusk then the dead come to reign over everything. The world doesn't end literally, but it might as well have, because now life is not really a thing.
What is less obvious is the rest of the endings. There are three fundamental unstoppable destructive forces in The Lands Between: Deathblight, Scarlet Rot and Flame of Frenzy.
Deathblight is sorta unavoidable because even in the better times, those who live in death were present despite the efforts of those who would seek to combat them. Namely Miquella and Fortissax.(I'm not sure if this next one is true, but I think it is stated somewhere, so take it with a pinch of salt) After the death of Godwyn, Miquella fought against those who live in death, but abandoned the cause and sought other ways to bring him back, like the Castle of Sol. Fortissax entered the Deathbed Dream and ultimately succumbed to the Death blight. So, The Age of the Duskborn, or rather the spread of Death blight is pretty much inevitable because you can't really do anything about Godwyn. He cannot be killed and cannot be revived.
Next up is Scarlet Rot. This one isn't exactly as obvious and kinda relies on environmental design. During the battle against Radahn Makenia unleashed the Scarlet Aeonia and ever since it's been spreading across Caelid, even creating an entire swamp in the middle. What I find interesting is that when you enter Caelid, you have to jump over a fiery wall. It's clearly meant to stop the Rot, but riding further you see more of these walls, meaning that the Rot was held back but ultimately not stopped. It spreads despite the best efforts of everyone else. And, personally I don't think killing Malenia does much to help it, since the Rot isn't her power. It's the power of the Outer God that chose her as the Empyrion. We killed her, sure, but the God is still alive and the influence is still present.
And at last, we have the Flame of Frenzy. Ever since Shabriri accepted it into his eye sockets it has been spreading through the Lands Between. Even people that have nothing to do with Frenzy can become Frenzied. Edgar upon losing Irene becomes Frenzied. Midra just does it of his own volition, fueled by Nanaya. There's a Frenzied village (2 of them, actually, one in Weeping Peninsula, one in Liurnia), Frenzied Towers that spread Frenzy around them and even a whole clan of Frenzied traders locked up in the sewers on top of the Three Fingers. As Melina says "However ruined this world has become, however mired in torment and despair..." implying that the world is indeed a little awful. Which will lead to Frenzy appearing again and again.
All this makes me think that even if you become the Elden Lord, there's really not much to be done about these three things. You're kinda fucked no matter what you choose.