That's what I keep questioning and why I've tried various methods. After screening resumes along with coworkers, at various companies I've worked at, we'll pre-screen or not, bring them in and ask them questions from their resume.

Resume says 'I'm an expert in SQL'. Great, lets start some every day foundational questions. What is the difference between an inner join and an outer join. Why might we use a varchar instead of a char data type? Why do we use indexes? What is the purpose of a foreign key? A good majority of the candidates can only answer the join question.

'10 years experience, senior dev in <main language>' can you write a function that returns the largest number in an unsorted array? Most struggle to even pseudo code it. Tell me something, anything about interfaces. Basic security question on SQL injection/xss/csrf/hashing/encryption. Without a doubt most have only heard of SQL injection and then they get that wrong. Most say hashing and encryption are the same thing.

I do blame myself, the failure rates are incredibly high. But when resumes looks great and onsite can't pseudo code a simple loop, or answer basic questions about something they claim expertise in, what can you do? Require and call references to make sure the the lead dev with 12 years experience and decent companies isn't lying? Because the result of most of my interviews appears that people inflate their resumes and flat out lie.