Evopsych doesn't disprove all of these theories and observations made by evolutionary biologists. But I haven't seen any other attempt to discuss human nature other than "God dunnit". It's certainly more logical than the blank slate concept, evolution stops at the neck and the human brain and the (il)logical aspects of it can't be studied.

Briffault's Law is just a coined term. It's a general observation, no different from saying that people are heterosexual. Homosexual people existing doesn't invalidate the general observation. You can still have intrasexual competition while still understanding that society panders to the biological sex that bears the most cost in reproduction (women). Same with a small percentage of men having the choice of the dating market. These things don't disprove the rule.

ETA: Alexander from DatePsychology did a video in the last few days regarding what seems like two contradictory concepts - hypergamy and assortative mating but they can co-exist and both be true at the same time.