I cannot speak to Catholics being more permissive of fornication, because I do not know it to be true or not. However, I can say that from my research- both from talking to older Catholics and reading documents pre- and post- Vatican II, that the church, although it did not change her teachings, significantly changed her stance on those teachings-primarily in “Loving God” vs. “Hell”.
It seems that the consequence of Hell was more frequently talked about and emphasized before. Sometime after Vatican II, for some reason, the readings about Hell subsided and more emphasis was put on God’s loving nature. The truth is, we need both. Jesus talked about both. Yes, God is loving, but we must be careful not to lose the way to him as a consequences of our sins.
I think Catholics are so very sure of God’s love and mercy, that we forget about the real possibility of Hell. It’s just not emphasized. I’ve known Catholic priests before- and sure, they warn you about sin, but Hell is just not much talked about. I think this may be an “over-correction” from older times. It’s like Catholics see the Father as a permissive one- so we go have sex outside of marriage and come back to confess and expect the Father to say "Oh, that’s okay son/daughter. We’re all sinners. You’re forgiven!, which is fine, except when it fosters an attitude of “it’s okay to sin because we can just confess and be okay” which is, in itself, a sin.
Older Catholics, please correct me in any of this if I’m wrong!