I think the main reason Liverpool haven't lost yet is not the defense but the goalkeeper. It will be interesting to see if he can continue like this in the second half and if Liverpool can move the game away from their goal. So far everything is going as I expected but it is not reflected in the score. Everyone was too enamored with Liverpool and this distorted the perception of their real strength.
Yes, in terms of defense it helps a little but indeed Alisson's slick appearance can block all accurate shots worthy of praise in this match. PSG reaped many obstacles to break into Liverpool's goal even in the second half they also dominated the course.
Liverpool reaped difficulties in this match because they were completely unable to build an accurate attack in this match, there were no shots on target that's why PSG was favored to win but they found it difficult to conquer Alisson. Salah also reaped difficulties in his space of movement he was guarded very tightly in this match, several attempts to build attacks always failed. Yes, we'll see if PSG can succeed in winning or have to be satisfied with a draw.
Edit : psg 0-1 liverpool