I don't think the article is arguing against being a generalist. It's arguing against selling yourself as a generalist. Being a generalist is fine. But when you

I don't think the article is arguing against being a generalist. It's arguing against selling yourself as a generalist. Being a generalist is fine. But when you're applying to a particular job, emphasize the specific skills that you have which would be applicable to that job. The advantage of being a generalist, of course, is that you have lots of specific skills that apply to lots of different jobs. You just shouldn't list them all on your resume all the time.