In the 1960s and early 1970s, people felt groovy. It was a symptom of their times. They were happy back then. They ate special brownies; they listened to psychedelic music; they went to college and kept repeating courses; they demonstrated and they discussed demonstrations; in short, their lives had meaning and purpose.
People don't feel groovy anymore. It's a symptom of our times. The world has grown weary, and people have grown weary with it. That's why the expression has disappeared from the lexicon, not because the expression is no longer groovy.