everyone deserves love and is sexually desirable (both of which are untrue)

Everyone deserves love and respect, but they're not entitled to receive it from anyone. You hope people give it to you, but you can't expect it to happen as a sure thing.

Not everyone is sexually desirable, just like not everyone is book smart and not everyone is good at sports. Humans have strengths and weaknesses. Some of it's hard work, but some of it is inherent ability (genetics). Embrace what you have and accept what you don't have, like any other area of life.

but the average, shy, girl-next-door type in school or at work is probably not getting spit-roasted every weekend

Lol why do boys think this is happening? Reading AWALT stuff? College-themed Porn? When I grew up, we only thought the sluts did that. The regular girls had boyfriends and relationships.

women have lots of sex all the time

Some don't. Many do... but most do with their boyfriends in monogamous relationships, not with random strangers.