Some history might help here.
When Adult Contemporary was first developed in the late 60s, it was largely a Top 40 playlist, minus the five or six hardest records of the week, with gold (oldies) that went back a bit further than the typical Top 40. Stations like WGAR, Cleveland and KFMB-AM, San Diego weren't soft. The format did very well, siphoning off young adults from Top 40. If anything, AC stations tended to skew a bit male, often also being the stations with the carriage rights for the local pro sports teams.
The soft approach was largely the invention of Jhani Kaye, who was programming KOST-FM, Los Angeles in 1983. He was faced with the challenge of taking a beautiful music station contemporary, so he went very soft and very emotional. It was one of the first stations to play almost entirely love songs. And it was a huge hit with 40-year-old women, which made it a 25-54 powerhouse.
KOST's success spawned imitators, to the point that Adult Contemporary became synonymous with "soft". But it was simply a phase of the format, which had established itself over the 15 years previous by playing (most of) the hits in a (slightly) more adult fashion than Top 40.
31 years have passed since Jhani took KOST down that road. The original audience is now 70. Today's 40-year old woman was born in 1974, graduated high school in 1992 and college in 1996. The old "soft" AC is irrelevant to her.
Jhani didn't prove that soft music was the answer for the format for all time. He proved that soft music was the answer for women born in the early-mid 1940s.
In the intervening time, male listeners have moved on (Classic Rock and even Active Rock do very well among men 25-54 and even older), so AC remains a female-heavy format. But Adult Contemporary is whatever the 40-year-old women of the moment want to hear. Right now, that's Pharrell Williams, Maroon 5 and Pink.