I'd say that the K-car was mediocre, not "worst" or even all that bad. The K-cars I knew had performance and reliability on a par with the competition in that price range, and were among the first to start to compete with Japanese cars on that basis.
Incidentally, I have long believed that the K-car was an undocumented part of the government bailout of Chrysler. My theory: Someone at the GAO slipped Chrysler a copy of the government's procurement guidelines, and Chrysler designed the K-car to fit them to a tee. That big contract definitely helped with Chrysler's comeback.
“no mention of the Chrysler “K” cars”
That little platform gave us the Mopar minivans, the LaBaron convertible, and a few other nice variants.
Then again, the Ford Fairmount of the late 70’s gave us the third-gen Mustang.
While the K-car helped Chrysler come back, it was the minivan derived from this very platform that really drove Chrysler’s comeback.