I tried this approach with a perfect resume and qualifications and got rejected after a long interview process. The problem is: there are always unknown element

I tried this approach with a perfect resume and qualifications and got rejected after a long interview process. The problem is: there are always unknown elements and biases in the process, and people were working differently than what I was used to. Still, lot of time went away for me, because I didn't want to go to other places. I believe this is good advice, but you still need multiple options, which means it's better to prepare but spare your own time: make sure the company invests in you as much as you do in the company at each step (even in the beginning...a cover letter is OK, but nothing more, like free work).