I concur. The entire game comes down to the interaction of the barrel and the bullet. ALL else depends (in the meaning 'hangs') upon that relationship. The remainder of the firearm has at least as much potential to detract from that relationship as it has to add to it. IMHO, the value of an intentional equipment feature is valued as much in what it does not do (detract) as it is in what it does do (add).
While I gladly acknowledge the many contributions the custom gunsmithing industry brings to the subject of accuracy, I see their main contribution as bringing correction to omissions that exist within the original basic core essence of the factory firearm. Because the factories manufacture to a meet set of priorities based primarily on profit, their offerings (mostly) meet certain minimum standards. That is not to say that whatever inferiorities exist are detrimental in either intent or effect, but it does leave significant room for improvement.
My own accuracy efforts are geared more toward working within the given set of parameters than to changing them. This is based in my own history of shoestring accuracy. When all you got is lemons, you can still make lemonade. Sometimes lemonade can be enough.
This just goes to show that when one finally overcomes one paucity (cash?), another becomes critical (time). It's always something...; but then it always was, and there's nothing to be gained in lamentation.
My preferred accuracy implements are handloading, and basic home gunsmithing employed primarily in eliminating the adverse effects of unfitted parts relationships; especially bedding. These smaller improvements, in and of themselves, can often bring the equipment's performance up to a level where the rifle can shoot better than the shooter. This is true, forgive me, in the case of most shooters. In no instance do I refuse to acknowledge the benefit of any methods or techniques intended to increase accuracy.
By the same token, I will often (usually?) pass up any I will deem to exceed a strict assessment of time/effort vs benefit. Yes, they work, but I need my fix before we all get old. The operative term here is old. I have it in spades. Of all my resources, time is the one I lack the most, and the one I value most highly. My fixes must not only work, they need to be most respectful of the time resource.
This all comes back to my earlier question, how much accuracy is enough accuracy? In my case, the answer is not going to involve diving down any rabbit holes.
For example, all my rifles possess chambers cut to SAAMI spec. They do not well support efforts aimed at improving concentricity. Accordingly, I make no efforts toward gauging or improving concentricity.
Do I sacrifice accuracy? Of course I do, but it is a conscious and willing sacrifice. Can a well bedded and well fed (load developed) rifle shoot to 1MOA without care to addressing concentricity. Yes. Can it do better than 1/2MOA/ Maybe; and besides, if I can maintain 1MOA out to a respectable difference, what to do I need a 1/2MOA rifle for?
So what to I gain in this trade off? First, I gain time. Next, as an Elder Fart, it behooves me to consider the next users of my firearms, my family which I hold most dear. I do not compel them to adhere to arcane and demanding shooting procedures. A SAAMI chamber can digest factory ammunition with some degree of reliance on inherent safety. I WILL NOT leave behind a rifle which might not do that safely. That's another aspect of responsible gun ownership that may be getting ignored far too much as we get older.
My point here is that for we less than ultimately committed devotees of accuracy, we walk, we run, and sometimes we gallop; and sometimes we stop at run. That's highly acceptable, IMHO; especially in the light that what we do is supposed to be fun, and not a chore.
Let us continue...
Greg