The accuracy vs. reliability dichotomy is a myth! For too long it has been believed that the only way to get good accuracy is to tighten the tolerances in a weapon until any speck of dust will foul it, this is BS! The two real keys to accuracy are the bullet and the barrel. If the bullet is uniform, well balanced and fits the barrel properly it will be accurate within the limits of the barrel. If the barrel is properly designed to fit the round being fired (bore size, rifling pitch, rifling geometry, ect.) you can achieve good results.
That being said, the overall weapon design can enhance or detract from accuracy. The standard AK (stamped 1mm thick receiver) has problem with flexing, in high-speed video you can see the action flexing (not to mention the rear sight bouncing up and down). This sort of thing will detract from accuracy, but milled and RPK (1.5mm thick receiver and larger barrel trunnion) style AK's suffer far less. The AK-74, with it's lower recoil and reduced mass parts suffers far less in this regard, and the 5.45mm VLD bullets are also far more inherently accurate.
The fact is that most weapons "Designers" are nothing of the sort! So-called designers take parts and pieces from different existing systems and mix and match them until they get what they want. "New designs" end up being nothing more than rehashed versions of existing weapons. Look at the G36, it is nothing but a version of the AR-18 in fancy plastic dress, same for the AUG, and the virtues as well as the faults of the previous design often creep in. True innovation in design is rare and often ends up being a novel way to screw up. Now, there is nothing inherently wrong with this approach, as there are only so many ways that a rifle can be made to work, the interface of weapon, projectile and human being properly achieved, but without a full understanding of all the factors involved will the weapon is more likely fail than succeed.
Our understanding of ballistics, interior, exterior and terminal, have undergone radical changes in just the past 30 years. The 5.56mm bullet was believed to tumble on impact (and it was this effect that the Soviets attempted to recreate with the 5.45mm) but in the 1980's we discovered that the bullet was simply disintegrating. Other designs and devices were thought to do one thing and then discovered to do something else. Double set triggers were thought to improve accuracy over conventional designs, now we know this to be untrue. It was believed that maximum contact between the barrel and the stock enhanced accuracy and now this has been proven false. Only when "common wisdom" was abandoned and a scientific investigation conducted was the truth discovered.
Instead of rehashing old ideas, we need someone to look at the totality of the weapon. Every aspect of operation, ergonomics and effect of every part of the weapon must be examined and tests conducted until the optimal balance of factors achieved IN THE CONTEXT OF DESIRED RESULTS. Only then will you get the best weapon possible, until your variables change and new designs required. I myself have attempted to do this and have designed a weapons system for military use. I believe that it would be far better than anything on the market today. I don't claim that it is perfect, and as I lack the wherewithal to build it, it is likely never to see the light of day, but it does show me that better results can be achieved in weapons design than have thus far been produced.
The bottom line is that the status quo in current weapons is far from what can or should be done. The AR-15 weapons family is the product of sixty year old ideas and technology, as are most weapon on the market today! We can do far more and achieve far better results IF WE WANT TO! It is the WILL we lack, not the ability.