"Our culture is sex-positive, so how come sex is so bad/hard/impossible?"

The truth is that sex-positivity, in the sense of talking about the positive aspects of good sex, is incredibly rare. Modern culture(s) is overwhelmingly sex-negative.

Conservatives are sex negative. They talk about sex as something corrupting, dangerous, sinful. Just try to talk to someone who goes on about "family values" about the importance for marriage of good, hot sex, let alone kinky one.

Progressives are sex negative. They talk about sex as harassment, grooming, exploitation. They only distinction they care about is consensual/non-consensual, but "consent" isn't close to covering the entirety of ethics surrounding sex, let alone actual eroticism.

Politicians in general are sex negative. All they know is to regulate and to outlaw (and to have unethical sex scandals). To them, sex is something you can throw people in jail for. People's private joy is not a political tool they can use. https://reason.com/2021/04/08/deceiving-your-sex-partner-would-be-a-crime-under-bill-backed-by-new-york-democrats/

PUAs are sex negative. They learn dumb tricks to sleep with desperate women who pretend to fall for them, neither partner having any respect for the other let alone the connection and intimacy that is required for sex to be really good and not merely the scratching of an itch.

Incels of course are sex negative. They are entirely out of touch with the pleasure and meaning of sex, both their own and women's. To them, it's merely an identity marker, all sex counting the same if it puts you in the non-celibate group.

Consumerism is sex negative. When "sex sells" it sells fuckability, not fucking. A million things can be sold to you promising to make you more attractive, but great sex between people who really connect can't be branded, commoditized, marketed, purchased.

Tinder is sex negative. It makes people fungible. Most men get nothing, most women chasing a few top men, and these men have little reason to invest in making sex good. Ultimately even the top men are unhappy — how can any man be happy surrounded by so many unhappy women?

The media is sex negative. A woman having a terrible sexual experience with Aziz Ansari is front page for weeks. If he was an attentive and skilled lover who left the woman ecstatic and uplifted even after a casual fling, we would never have heard about it.

Sex negative culture perpetuates itself. People internalize that sex is bad, and opt out of dating altogether. If they do date, they feel no impulse to invest in being good lovers for the sake of their partners or even in exploring how great sex really can be for themselves.

Anyone talking about sex that's mutually pleasurable, spiritually uplifting, and that meaningfully connects people is seen as contrarian or subversive. Sex positivity, throughout most of history and equally in 2021, is counter-cultural.