Has it really been lost if you can access it through Ouraboros?
Perhaps you could echo it? I realize things can start to get messy when you have a 'present' day contact giving missions in the past, but considering how few missions actually go in there perhaps it wouldn't be that much of a bother.
You're absolutely right. My main reason for disliking Ouraboros is that I'm locked within a taskforce like team to where I can't easily invite people to do arcs. You're also forced to exemplar for the content and lose abilities, which is doesn't feel great a lot of the time. I've seen before that people have mentioned that if we were to have zones scaled to 50, they would have to make new types of mobs. There's no hellion or outcast that has abilities that would threaten a full incarnate team, so I understand why they did that.
EDIT: New Idea to Go Along With this.
Maybe use Ouraboro's less as a way to replay earlier content and a way to do challenges as a new hardmode? Something like m+ affixes on wow.
Like:
1) All mobs have fire aura
2) All mobs explode when dieing
3) Mobs hit for 50% harder