The unemployment level is currently 6.06 million. The part-time who want a full-time job currently number 4.87 million. The number not-in-the-labor-force-want-a-job-now is 5.18 million in May 2018. Add 'em all up and there's 16.11 million people right here in America for the 6.55 million job openings. The employers don't fill the jobs because they can, otherwise the situation wouldn't persist.
Not enough workers? Like hell there aren't.