There's a lot wrong with that article, you're right. Another way the article is BS is that Joel assumes that it is only possible to get good candidates by being the employee's first employer, since "they already have jobs. Stimulating jobs. Jobs where their employers pay them lots of money and do whatever it takes to keep them happy." It's impossible! Here's a pro-tip for all you hopeless employers trying to hire these inscrutable "top engineers", who are unfairly entrenched in their existing jobs. Ready to be blown away? Write it down, who knows when this post will go away!
Offer them a stimulating job, and pay them lots of money, more stimulating than their current employer, and more money than their current employer.
There you go, glad I could help.
If there is this "floating population of applicants in your industry that apply for nearly every opening posted online" as Joel puts it, then I'll offer that the software job market is also flooded with a floating population of "dog jobs" that are uninteresting, low pay, crappy company/work conditions, etc. that never get filled without paid recruiters spamming thousands of people daily. When you search job boards, nearly 100% of the jobs are such. When you get another LinkedIn message, it's more than likely a dog job. Don't get me wrong, I like hearing from recruiters, and I appreciate the opportunity of getting a heads up about the kinds of jobs that are out there, but the pickins of GOOD JOBS, jobs that I would leave my employer for, are pretty slim.
Improve job quality and you'll improve your candidate pool. Pay bananas, get monkeys.