They're still only tangentially related to the game's primary revenge narrative. Naoe and Yasuke have complete arcs in the base game. I don't disagree that it's a bullshit business tactic and that shadows is probably the worst ac in that regard, but it does have multiple endings more or less on par with Odyssey or Valhalla in terms of wrapping up loose threads. It's assassin's creed, they all leave dozens of loose threads.