The set-up isn't suiting us. When there are so many bodies in the middle, and Saka is successfullu held down by the double-team, I think we always see the same issues:
Partey is the one that has more time and space on the ball, and he doesn't have the brain for playmaking in the way Ødegaard does. He's predicatble, takes too long and can't see more than one pass ahead.
Martinelli can't beat his man from a standing start and therefore does not have to be double-teamed - allowing them to remain compact. Zinchenko doesn't effectively overlap.
Xhaka can't influence the game because his touch and quick passing doesn't hold up in the heavy congestion.
In these situations I think the most effective change we can make is switching Xhaka out for Vieira (though Im not sure Vieira is necessarily up to it right now, its more about the tactical change). If we have the same control we had in the first half, and they continue to sit in, Xhaka is too advanced to be useful when they force turnovers anyway, so I don't think we lose much defensively.