The problem is, you can’t repent if you don’t have a clear understanding of sin. Many Catholics have little doctrinal formation, and in many parishes they hear only about “sins” like poverty, inequality, war, religious hypocrisy, and so on - in other words, the actions of other people besides the ordinary person sitting in this congregation.
In my diocese, confessions are more available than in recent years. “The light is on for you”, both in terms of convenient times, and priests who are not going to condemn anyone. The sad reality is that there have never been so many friendly, empty confessionals. People are staying away, not because they fear anything, but they just don’t see any reason to go. Nothing is absolutely right or wrong, everything is relative.
I would say that the Truth, Repentance, and Forgiveness are at heart of the Gospel.
