absolutely no reason to ever use anything other than an LMG

LMGs actually suck in this game so much.  They're far more inaccurate than ever, suppression no longer exists in a useful sense, and the ADS time takes about 12 days in comparison to every other weapon.  Their ammo attachment costs are INSANE as well, since most of them have been dropped to a 50rnd or less, and just trying to get to 100 like an LMG should have takes ALL of your attachment points.

After hundreds of hours in this game, I would say LMG is the least likely weapon to come across, and the least likely to kill you due to their slow fire rate and moronic levels of recoil and inaccuracy.  Most SMG's will easily outperform an LMG at any range, and since they generally take maybe 1 second to reload, they are easily able to counter the large initial supply of some of the LMG options.