Short story, possibly from Omni, 1970's, protagonists change sex via a pill

I believe the story is called The Second Generation by Rachel Pollack. There is a scan at the Internet Archive.

I had a similar memory of a similar story, but I think it was what @Binary-Worrier mentioned: "Changes", by Neil Gaiman.

The synopsis from GoodReads sounds about right:

A scientist named Rajit, devises a cure for cancer.

And the story was basically people are taking pills to cure cancer, but it also resets their chromosomes to either an XX or XY expression. And once the treatment becomes commonplace, people start taking the pills to change their sex at will.

The scene that stuck out in my mind was the very end. I think the doctor was too old to take the treatment, or otherwise refused it, and he's on a beach seeing everyone just simply enjoying their humanity for what it is, no matter their underlying sex or gender.