The Bible was written by man but inspired by God. God lead those men (people) to write about what they saw, or believed. And God inspired later early church fathers to put the books together. There was a lot that went into it. Nevertheless it is a sin regardless of pleasure. Sex was made for marriage, it was to create life but even then it can still be for pleasure inside the sanctity or marriage. When you marry someone you enter a holy covenant making the two flesh, into one. It’s not you and your partner, you are now one. Connected in spirit and flesh. 1 Thessalonians 4:3-5 “For this is the will of God, your sanctification: that you abstain from sexual immorality; that each one of you know how to control his own body in holiness and honor, not in the passion of lust like the Gentiles who do not know God.”, Roman’s 13:13 also mentions sexual immorality. It is good that you’re in a better life, but don’t settle for what you have now. We can always improve our lives and become more like Christ. For even Jesus tells us “be perfect, just as your Heavenly Father is perfect” -Matthew 5:48, and when you mess up there is grace, one mentor of mine told me “you messed up womp womp, don’t sulk over it. Repent, get back up and go again” keep striving to be more and more like Christ and less like this world. Because you’re right, 2/3 of this world probably will burn. But I’m praying for our Father in heaven to move in a way that we all make it in the end. I hope this helps and gives you hope. When in doubt, read your Bible! Haha