Ask HN: How do you *really* get a good Software Engineering job?

It seems like anything I do is never good enough. I can know how to code in multiple languages and provide decent coding examples. But, there is always one little thing that I didn't have in order to get the job. It feels like job postings are not very honest at what they are looking for either. An example would be of a 'Frontend Engineer' job posting that I got an email response back from the hiring manager for, and he asked for a link to a fully functioning and non-trivial web app that I had built before. Wtf? I have not built that as of now (even though I am confident I could). And it would not have been in the companies preferred stack anyways. I just want to know one thing: WTF do hiring managers actually want? And why do they almost never seem know themselves? Sorry for the rant but it just seems like this industry is a load of bullshit.