Why did Christopher Plummer hate making this film so much??

His official explanation is that people don't recognize any of his other acting work. Sadly, that's a common problem with famous actors. They take a lot of pride in all their work, but only get recognition for the few performances that everyone watched, such as that one famous film, or some popular thing they did on television. He probably also got tired of the same old questions fans would ask him about "Sound of Music."

Reminds me a bit of Robert Reed. He saw his best acting roles as being in Shakespearian plays or serious TV dramas. Instead he is best remembered for being the father in the Brady Bunch. It's no secret that he hated the TV show.

https://www.looper.com/328225/christopher-plummer-actually-hated-the-sound-of-music-heres-why/

As for the reason for Plummer's contempt, he gave a few explanations over the years. Sometimes he expressed disdain for Captain Von Trapp: "I was a bit bored with the character,” Plummer told The Boston Globe back in 2010. "Although we worked hard enough to make him interesting, it was a bit like flogging a dead horse. And the subject matter is not mine. I mean, it can't appeal to every person in the world. It's not my cup of tea.” In 2011, he went into further detail at an actors' round table organized by The Hollywood Reporter. Citing The Sound of Music as his toughest role — strong words from the guy who played the emperor in Starcrash — he called the movie "so awful and sentimental and gooey," and recalled that he "had to work terribly hard to try and infuse some minuscule bit of humor into it."

Plummer would spend the majority of his life avoiding The Sound of Music whenever possible, turning down offers to appear at the film's 40th anniversary reunion before relenting and joining his fellow Von Trapps on The Oprah Winfrey Show for the 45th. Meanwhile, on the other side of the coin, there was one role that Plummer always regretted not playing. In an interview with Conan O'Brien, he expressed regret over the fact that he had been offered the part of Gandalf in Lord of the Rings but turned it down. "...three or four years in New Zealand," he said, "I thought maybe there were other countries I'd like to visit before I croak.

Plummer got an all-expenses-paid trip to Saltzburg, and a huge paycheck for playing with young Julie Andrews and Eleanor Parker all day every day. My heart bleeds for the poor bastard.

I love this movie, it's wonderful and 99% of the time it will make me happy. However, at some point, it always hits me "Everyone is sitting there, supposed to be excited about hearing kids sing about jam and bread repetitively?" Maybe that has something to do with it.