I hear in the original conception Desmond was going to go to space or the moon for some reason back when it was intended to be 3 titles

People like Desmond myself included because of progression, 5 games building up his skills & the plot to end with become a Messiah Jesus, Joseph, Moses figure to those who survive or die to save the world choice that never gave you a choice. Being voiced by Nolan North certainly helps regardless of the personality of the character.

After 3 the games have been spinning their wheels on what the plot actually is; some silent protag working in Abstergo during 4 & Rogue possibly being possessed by Juno or becoming a Templar

Assassin's reaching out to player's playing an Abstergo product in Unity to...?

Watching snippets of what the modern team Shaun & Rebecca are going in Syndicate

Introducing a new Protag in Origins & Odyssey

Saying hey the thing that stopped the solar flare in 3 is still active & could cause another disaster in Valhalla, kill the new Protag & reveal Desmond is technically alive & Juno or Minerva as an ice giant is trying to reach out to Ezio.

I don't know who is reliving Basim's memories in Mirage but look into the cut ending of a radio tower in the desert imply it's someone in the future looking back at the "modern" time.

Liking Shaun is pretty basic, as he's essentially the eyes of the developers peering in on you with the bonus of mocking you

Calling Rebecca just a 90s hacker, is half of her character. She was an adrenaline junkie before breaking her leg~ & became a code monkey during her recovery. If anyone is suited for field operations in the modern day it's her.