Having lost the first leg at the Parc des Princes 3-1, PSG faced an uphill battle to avoid going out in the last eight for the third consecutive season on Tuesday.
But PSG never came close to mounting a spectacular comeback at Camp Nou, with a double from Neymar securing a 5-1 aggregate win for Barca.
And Luiz told ITV: "They were a better team than us in both games. They controlled the games and deserved to qualify. They had a great match and took opportunities to score when they came.
"All the teams have spent money. We did very well until here, but against Barca we couldn't play at the same level. This is life."
The former Chelsea man expects PSG to fare better in next season's competition, however, adding: "We need to improve and next year we will challenge for the Champions League."
