Laporte is a good defender, but he is not the greatest against elite. He's got 5-6 BIG mistakes at UCL (2 Tottenham, 2 Lyon, not going out to stop Vinicius last year + his stupid penalty), and even this year against Nottingham the intensity of his defense in the goal was laughable. Laporte is a defender that doesn't have the concentration and intensity (and I would say the love for defending) as Dias or Ake.
Laporte is a classy defender with great build up from the back, but his defense is not that great, and I think going by his history in the biggest stages, being worried about is logical.