It hops all over the place. Some say it's today's stuff that's the worst; I've encountered a lot of trash talk about the Bangor Punta period; even read an article that said the late '80s to early '90s was for some reason S&W's lowest point.
I've given up believing or caring, and don't think there's ever been a best or worst era -- each has produced its share of superb revolvers, and each its share of lemons. It all comes down to the specific gun.
Before people were upset that barrels were no longer pinned. Now it is the lock (though with the Centennial models there is the no-lock option).
Around here the biggest issue I come across with new revolvers is Charter Arms with cylinders stuck closed. The solution is always something simple.
I see the lower quality statements as an internet myth. As much as people gripe about MIM, fact is that functionally the biggest difference from now and a couple decades ago is that now everyone gripes on the internet if they get an issue.
I'm no expert, but have been buying guns for some 18 years. A few new guns have had minor problems, but none that I couldn't live with or that couldn't be easily rectified. Out of all of them so far S&W has been the best to me.
Unfortunately it is consumers that have driven prices down and thus simplified production in modern times. These days the price difference between most revolver manufacturers is not nearly as wide a margin as it used to be.
Despite this most experts believe that the production consistency and tolerances are better than ever, so despite much of the romanticism being gone from the days of old they're still putting out a good product.
It's good to see they're taking care of customers with decades old guns. I put a few hundred rounds through mine fairly quicky as that seems to be when most cracks occur. So far so good. If it gets a free replacement if it cracks in thirty years, that's ok.
On repairing fatigue cracks in aluminum alloy, that'd be an exercise in futility.