I don't think this is quite the same as what the Ascians were doing.

The Ascians wanted to kill the present world to restore their world of old. But at lest this was potentially viable, barring the fact that Emet himself admits they never would have made it to Ultima Thule to confront Meteion with their methods.

The fact of the matter is, Living Memory is unsustainable. It is not viable in the long term. Sphene can only keep it going by killing our world and draining its life energy. And then she'd eventually have to go to the next and the next, butchering world after world as her afterlife of Endless continues to swell out of control. Emet vs Scions was Emet wanting to kill the present to revive his past. This is wanting to kill the world to keep the unsustainable ghost machine running. Regardless of whether the Endless themselves were going against nature or 'should' or 'should not' exist in general, this system had to go. Alexandria was coming to US wanting to devour the Source's life source. Emet-Selch was, in a sense, a foil to Thancred who had to let go of Minfilia, the old, and learn to fully embrace Rhyne, the present. Here, Sphene is a dark reflection of Wuk Lamat, someone whose love for her people drives her not to heroism and reaching out, but to monstrous, unsustainable acts out of love.

We do have some lines about how we shouldn't feel bad about ending these simulated memories but the characters don't treat them like that. Erenvile and Krile certainly don't dismiss them. Wuk Lamat wants to take the time to know and understand them before shutting them down. Erenvile's mother despite the comments on her own existence and wanting it to end, wants to have some last minute bonding with her son before she goes. The bonding between Krile and her parents is not presented as meaningless because 'it's not really them.' I feel like she's trying to console the characters more than the player.

What this really reminds me of is helping lost spirits to move on. That's the kind of vibe I get from the side quests there. We have to shut down this machine, to save not just our worlds but other reflections. But we can still be as humane and compassionate as the situation permits and ease their passing.