is attack on titan (shingeki no kyojin) episode 61 filler?

Following Marley's victory at Fort Slava, Theo Magath, Zeke Jaeger, and Colt Grice attend a meeting with their general, who is displeased to hear that the rest of the world is spinning the near defeat of Marley's Titans into a positive for the Mid-East Allied Forces. When asked for his opinion on the matter, Magath is forced to admit that the era of Titans is coming to an end.

Their complacency and reliance on Titans have caused them to be underdeveloped. As aircraft advance, the Titans will be unable to do anything but watch.