There's a fair disparity between groups of Millennials with regards to communications ability. And, by the by, it's absolutely strange to see conversations I constantly have professionally showing up on these forums... my worlds are mixing!
The culture gap between incoming Millennial workers and their managers is largely responsible for this. Many in this group did not receive adequate coaching and preparation for a professional workplace during their internship experiences throughout college, or while tending bar to pay their bills. Very few managers want to offer that basic professional coaching in a supportive fashion for incoming young workers.
Some of this is actually our generation's fault (Xers) - having brought a largely casual and friendly atmosphere into the workplace culture (when did casual Fridays turn into casual Mondays through Thursdays as well? Yup, that was us), as the managers most interns are working with are Gen X, and are not coaching them on formal professionalism but rather choosing often to "let things slide" since they're so young, just an intern, well-intended, etc. Coachable moments become jokes rather than teaching opportunities.
On a positive note, however, there are large percentages of Millennials that are incredibly hard-working, communicate professionally, and are looking to improve their generation and the workplace at large. I get to work with those students, primarily, and they're great.