Some companies are unable to judge talent. Others are able to judge talent quite well, and those companies still have difficulty hiring (mainly at the mid to senior level). That is my argument for there being a talent shortage.

Re job postings, most jobs are not filled through job postings. If you want to find a job at a company that knows how to hire, you will have much better luck if you find the opening through networking or a referral. I have literally never got an engineering job through any other channel. (Note that this does not serve as evidence toward your indictment of HR, most networking/referral hires still go through HR to at least some extent).