Kroos played a key role in recent successes at the Allianz Arena, but the 24-year-old departed for Real Madrid this summer after refusing to sign a new contract.
Lahm has called Kroos "an excellent man", but insisted that the Bavarians will always move on from the loss of key players.
"We have so much quality at Bayern that it's difficult to weaken us," he told Kicker.
"I do not mourn Kroos. I've been around at Bayern long enough to not grieve for players leaving, even if Kroos is an excellent man."
Bundesliga champions Bayern face English champions Manchester City in the Champions League this week.