Cope. Also, thinking that casual sex is the standard is self defeating if pleasure is the goal. Casual sex is cool because it requires very little of the participants. Get off and get going, everyone is somewhere between satiety and scratched itch in terms of payoff.

Long term partnered sex is like an ongoing conversation about pleasure and likes and dislikes and leads to way more fulfilling encounters. It can also just scratch the itch but has more upstream pleasure potential ime.

Sex with another person was in some ways disappointing when compared to masturbation and porn. I value emotional intimacy and you can’t get that by masturbating, but if OP is interested purely in physical pleasure then he may in fact be better off on his own. Obviously your mileage may vary - lots of other people do enjoy casual sex so I guess they must get more than I would from it.

(I’m single now but in case a future partner sees this: you’re different and I definitely enjoy sex with you more than anything else.)