The Bundesliga really was incredibly strong in the late 70's/early 80's and it's a bit of a shame that our teams regularly fecked up CL finals despite being the 'better' team. I was always surprised that it was that highly rated by France Football though, we had 6 consecutive Ballon d'Or winners from 76 to 81 (Beckenbauer, Simonsen, Keegan twice, Rummenigge twice) and only one (Sammer in 96) in the following 33 years
. As an example how strong the Bundesliga was, we were really dominant in the UEFA Cup for a while, 3 German semifinalists in 79 when Gladbach won it, followed by an all German semifinal (crazy, I know) in 1980 when Frankfurt won it.
I agree that it was a time inbetween superstars though, Cruyff, Beckenbauer, Müller were past their peak and the Platini, Maradona era was only about to start. Rummenigge was probably the only exception, but Keegan and Simonsen are a bit underrated because the Bundesliga always lacked that special flair that attracts worldwide attention, doesn't capture the imagination of foreign fans. The Gladbach side from the 70's is easily one of the most underrated teams ever because of it and were unlucky like few other teams to never win the European Cup.