Endwalker's story had me, but lost me. Ethical issues especially (spoilers)

[Ryaz]

Er, G'raha didn't return to any future. He stayed right where he was.

And whether or not we'd return to our future is a tossup. Actually, I can't remember how we did that in the first place. All the technology needed to send us back in time... we didn't exactly stick it in our pocket and take it with us. How did we leave Elpis?

His soul and memories came back with us to our timeline, he didn't end up back in the other branched path, so it does show that they can end up in a different timeline. Though I suppose that could be explained away due to him being in the crystal.

[Veloran]

His soul and memories came back with us to our timeline, he didn't end up back in the other branched path, so it does show that they can end up in a different timeline. Though I suppose that could be explained away due to him being in the crystal.

The First and the Source aren't different timelines, they're just two shards of the sundered world. The Eighth Umbral Calamity era is a different timeline, and a lot of people seem to be under the impression that G'raha going back in time destroyed that timeline, when in fact it only created a divergent timeline, ours.

A major issue I have with Elpis is that in theory, they could all be saved simply by creating another divergent timeline. Even if the Ancients failed to do so, WoL could simply go back and stop Meteion themselves. Implicitly, the only thing preventing this from happening is that unlike G'raha, WoL lacks the personal investment to expend the effort of trying to save them. Which would run contrary to WoL's character, practically making them a bad person by way of laziness.