Then the company should better advertise more exactly in its job ads what they expect from their candidates so that less unqualified applicants submit their app

Then the company should better advertise more exactly in its job ads what they expect from their candidates so that less unqualified applicants submit their applications (while - of course - not preventing suitable candidates to submit their applications). Is this nontrivial? Surely it is; but that's why HR is a distinctive position in most companies. If you want to learn more about this topic, begin reading about statistics - especially type I errors and type II errors, since this is the mathematical formulation of the topic I was talking about in the previous paragraph.