With the design of the M14. And that was to put a full auto switch on it. By doing that, they tried to make it something it never should have been, which is why 90% of them had the switch removed and the "selector lock" installed, making it semi only. If they hadn't fooled with the full auto in the first place, it would have been hailed as a great rifle and a worthy replacement for the M1.
Instead many people just look at its problems as a select fire weapon, and its short service career (as a general issue rifle), which was cut short by politics and changes in what the service wanted, not due to any fault of the rifle's design.
I have used the M14, FAL, G3, HK 91, and M1A, and of the rifles I can legally own, I prefer the M1A. It has advantages for a civilian owner over the G3/HK rifles, especially if you reload.
I have never used one of the AR rifles in .308 (yet), and so withhold judgement, butr I have extensive experience with the AR15/M16A1, and some with the A2 and the semi M4s, and while they are better than they used to be, they are still poodle shooters.