It was never going to be perfect, of course. The finale might have been a bit rushed, more time might have been spent on a few of the characters beyond the Scotsman, but in its early seasons Samurai Jack never lingered too long on any one place or setting. It knew just when to see its way out -- when you were wholly invested. And if Ashi disappeared, that means all of Jack's friends in the future and all of their lives also disappeared. They mattered in the end, of course, but only to Jack. They'll only exist in his memory now, making good on his point to Ashi earlier in the season, that all he has left of the past are memories. It's bittersweet and poetic that the show would end with him living out that same fate, but for those he left in the future, those same characters like the Archers or the apes who "jump good" that the series' diehard fans spent years getting to know.