Don, there is some substance to what you say, in as much as turning out such large numbers of guitars across a vast range of models, there are going to be some QC issues, simply down to the fact that wood is such a variable factor.
I am lucky enough to have some very good Martins from recent years ( D28,D41,00028VS and 00028EC ) all of which stood out from the rest of the pack, I have also had a few, including examples of the aforementioned models that struggled to come up to scratch. The four Martins I mentioned all hang on in there against the smaller shop guitars I also own and play.
Knowing enough about wood selection, storage and ageing, I note that some of the more significant problems with odd guitars coming out of respected name factories is down to less than top grade woods. I suspect that due to turn over of wood stocks everything gets used, and sometimes too soon to have fully seasoned ( I have recently had two custom shop Gibsons where the ebony boards ( ebony being prone to dry out ) have contracted /expanded significantly within weeks of shipping. This suggests a use, in some examples of woods either, lacking stability or not having fully aged before use.
The general grade of woods used back in the Golden era were very high on production models, while now it seems that to get the best, it is safer to go to the small shop luthiers, where wood selection is generally high and instruments are built to bring the best out of the wood, rather than to specified production quotas.
Having said all that, it is possible to find a very good Martin these days, as,if anything, the existence and success of Collings etc. have forced up the standards from the old guard.