There was much I disagreed with in this post, but I had a hard time even addressing a single point, as I felt that it was a bit all over the place. I decided to first try to condense it a bit. In the end I realized that I understood the author a bit better. I still don't agree, but I get where he's coming from. Here's my paraphrased summary.
So the author originally found much satisfaction in his exploratory, entrepreneurial, and hacking activities, as it offered a counter-balance to the corporate culture that he perceived as shallow and alien. It didn't matter that his ventures ended up as failures, he found something worthy out of the process.
Sometime later he had a change of heart and decided to pursue a "career". He was then confronted by a clash of culture when he realized that all his tinkering didn't matter to HR.
Now, he's a manager and he understand HR's perspective on reality. He gives you a glimpse. His time spent working on projects was a waste at best and a liability at worst. Companies don't need innovators or free thinkers, they're afraid of them. What they need are good soldiers unburden with ideas of freedom. Exploring new shiny stuff does not make you appealing to HR, your capacity to endure the grind does.
The author offers some philosophical digression where he posits that side projects, much like the theoretical stuff that you learn in school, serve to expand your mind, but don't let them delude you into thinking that you can make that enriched vision serve you in the real world (of employment I suppose).
True valuable experience comes from getting a first job and to do that you should brush up on your DS & algo theory and do coding exercises. Don't expects all your shallow side projects to come to your rescue at your next technical interview.
The author concludes that if you want to make things easier for yourself, you should get a job. It will free you to be yourself, to go fishing, to have a life. If you still want to work on some side projects, you'll do so because they truly matter to you, not because you think they will be strategically helpful in your career. It will suck becoming dependent on a company, but it's the price to pay to be safe from the relentless competition in the job market.