No, and it wasn't crappy in 'Nam either. A lot of the criticisms for its performance in Vietnam had to do with using the incorrect powder in the cartridges, and also neglecting to teach the grunts to clean their rifles regularly (pencil pushers at the Pentagon foolishly thought it never needed to be cleaned). Also, the addition of the forward assist on the A1 helped.
Today it is a great assault rifle. Most criticisms of the AR-15 platform are due to the fact that it cannot reliably function in sustained full auto for long periods of time (i.e. several hundred rounds) without jamming. No kidding it can't. It's rifle, not a light machine gun. It isn't made to fire in sustained full auto. The AR-15 is designed to be shot primarily in semi-auto with full auto only intermittently. It is designed this way because of the predominant US combat philosophy since after WWII.
“It isn’t made to fire in sustained full auto.”
Bingo as they say here at FR. If M4 met the requirements of sustained 400+ round firefights then it would weigh 15-25 pounds like the current inventoried/deployed weapons do that can sustain that volume.
Infantry works as teams. Fire team, squad, platoon, company, battalion, etc...each component has a balanced arsenal of weaponry to meet the missions they are SUPPOSED to be assigned. Sustained fire is the province of a few squad weapons keeping an enemy pinned down while the riflemen maneuver close enough to grenade the bastards. Or for the mortars, arty, or air to respond and end the disagreement in a civilized manner.
For specialty applications like long range (400 meter+?) accurate anti-personnel shots, there also already exists in the US DoD inventory many a fine tool in many fine platforms and calibers.
But what the heck do I know and I don’t feel strongly about it.