Enfield never quite recovered after Churchill yanked the rug out from under them with the EM-2 rifle in 1951. It was more than a generation later when they started working on the SA-80, but by then they had lost all the "institutional knowledge" of gun-making as their workforce moved on or retired.
The engineers who designed the SA-80 did a good job, but that's only part of a new gun platform. Guns aren't complicated, but most new designs require a lot of fiddling to make them run right. The US M-1 Garand took more than a decade of twiddling, first to make it work, then to make it reliable enough to use. And then it took another decade to graft a box magazine onto it to make the M-14. So Enfield's guys were hardly slackers.
The original American Armalite M-16 rifles had problems; Armalite's engineers were good, but not good enough to solve the operation and manufacturing problems quickly enough to get a government contract, so Colt wound up doing the tedious work of ironing out all the problems and the actual manufacturing.
Enfield was in Armalite's situation, but the British small arms industry was basically dead by the 1970s; H&K became Enfield's Colt, ironing out the bugs. It wasn't a matter of competence; Enfield's guys could have gotten everything tweaked eventually. But the government wanted its rifles *now*, even with the problems. Enfield wound up shutting down in the backlash, and HM Government had to pay almost full price *again* for some foreigners to deal with the problem. Which was, in the end, all of its own making, all the way back to 1951.
Still, it's a right-hand-only firearm, and therefore basically just an awkward club to some of us left-handers. Which was peculiar, since Britain has one of the highest percentages of left-handed people.
