Sex without attachment would be like scratching to feel itchy.
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The Buddha was more a bit more colorful in his teaching and compared the dangers of indiscriminate indulgence in sensual pleasures to embracing a burning bonfire:
AN7.72:1.6: “Mendicants, do you see that bonfire burning, blazing, and glowing?”
Sensual desire is quite powerful. And just like a bonfire, sensual desire also grows when fed and relished. Sensual desire is latent, like a tank of gas waiting for a match. For sexual pleasure in particular, our genes open up and give us access to that tank of gas at a certain age. We can't really be unattached to sensual desire without emptying that tank of gas. Emptying the tank of gas is a bit of work, so putting more gas in the tank to light a fire seems a bit like scratching to get itchy. It would not makes sense.
Fortunately, sensual desire is the fourth fetter. There are three others fetters that precede the fourth fetter and with the relinquishing of each fetter, suffering decreases:
DN33:2.1.20: Five lower fetters:
DN33:2.1.21: identity view, doubt, misapprehension of precepts and observances, sensual desire, and ill will.
It is indeed good to consider others instead of only oneself. When we consider the welfare of others, we can let go of identity view.