Of course it is.
There are many much better options for that same platform. The military almost adopted a .270 caliber... what was it, the 6.8 or some such? It was supposed to be way superior to the 5.56, ballistically.
There are also other very popular options, such as the .300 Blackout, which gives the same power range as the 7.62X39, with a smaller case head to fit the AR bolt face.
I have a 6.5 Grendel, which uses the same case head size as the 7.62X39, which works well in an AR.
I think the military is too heavily invested in the 5.56, though, so they are making it somewhat better by going with heavier bullets, which improves penetration and terminal ballistics.