Contrary to popular belief, Sin is not anything Pleasurable, Delightful or Wonderful, lets get to the chase,
1 John 3:4-10
" Everyone who practices sin also practices lawlessness; and sin is lawlessness. 5 You know that He appeared in order to take away sins; and in Him there is no sin. 6 No one who abides in Him sins; no one who sins has seen Him or [b]knows Him. 7 Little children, make sure no one deceives you; the one who practices righteousness is righteous, just as He is righteous; 8 the one who practices sin is of the devil; for the devil [c]has sinned from the beginning. The Son of God appeared for this purpose, to destroy the works of the devil. 9 No one who is [d]born of God practices sin, because His seed abides in him; and he cannot sin, because he is [e]born of God. 10 By this the children of God and the children of the devil are obvious: [f]anyone who does not practice righteousness is not of God, nor the one whodoes not love his brother.
So sin is basically Lawlessness/Breaking God's law.
Now what is The Law?
Matthew 22:34-40 - "But when the Pharisees heard that Jesus had silenced the Sadducees, they gathered themselves together. 35 One of them, [a]a lawyer, asked Him a question, testing Him, 36 “Teacher, which is the great commandment in the Law?” 37 And He said to him, “‘You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.’ 38 This is the great and [b]foremost commandment.39 The second is like it, ‘You shall love your neighbor as yourself.’ 40 On these two commandments depend the whole Law and the Prophets.” - God(YHWH(The Father and The Son and The Holy Spirit)
Matthew 7:12 - "In everything, therefore, treat people the same way you want them to treat you, for this Is the Law and the Prophets." - YHWH(The Father and The Son(Jesus Christ) and The Holy Spirit)
So to sin is to Break The Law, which is Treat others the same way you would want them to treat you, it's to break The Law which is to Love Everyone.
Sin is to harm another, plain and simple.
So no, no matter what any atheist, unbeliever, so called believer says, sin in Christianity is Not anti-pleasure or an imaginary concept
It's not Fun, and it's Real
Sin is basically... Harm.
I'll end with Colossians 2:20-23 - "If you have died with Christ to the elementary principles of the world, why, as if you were living in the world, do you submit yourself to decrees, such as, 21 “Do not handle, do not taste, do not touch!” 22 (which all refer to things destined to perish with use)—in accordance with the commandments and teachings of men? 23 These are matters which have, to be sure, the appearance of wisdom in self-made religion and self-abasement and severe treatment of the body, but are of no value against fleshly indulgence."(This passage proves that flesh doesn't mean literal flesh, but is a term, flesh means Harm. we should not indulge in harming other people)