I feel the same way, I've still yet to hear it besides Youtubing it myself recently
Probably because in a year that saw successes of Megastars like Drake, Beyonce, Adele (the very beginning), Rihanna, Sia kinda, etc, the Chainsmokers just kinda... pale in comparison in terms of starpower and impact, even if Closer spends 17 weeks at #1. Oddly, I had heard DLMD a lot more when it was smashing, but that's of course anecdotal. It also doesn't feel anywhere CLOSE to the league Uptown Funk, Happy, We Belong Together, We Found Love, etc did in terms of ubiquity.