This is very true, and seems to be a worsening problem that DL is aware of.

I have had more and more frustrating experiences with low TSA staffing, dead mobile phone scanners (not properly charged by TSA, forcing people to return to the counter for paper boarding passes) and surly and unapologetically-slow ID checkers.

DL staff fight with them regularly and try to manage the lines, but there's only so much they can do.