Chuck,
As one who went through a Smith armorer's school way back, the bar's called a babbitt, I'm familiar with it, I've owned one Smith & one Ruger that needed it, and it has been around for a long time.
Over-torqued barrels are not entirely a recent phenomenon, with either brand. But, it does seem to be happening much more often on new Smiths than I ever recall it happening several years ago.
Your experiences may be different.

The 686 I have here is over-torqued, the two .44 Special TR Model 21s I had here that were returned to the maker unfired had the same problem, along with the barrel constriction on one, forcing cones that failed a GO/NO NO gauge on both, a gap between the grip panels almost big enough to insert a dime on one, and the engraved drag lines on both.
The problems with the front sight blade height on the first .45 ACP 22s should have been caught at the factory before ever leaving the factory.

That engraved drag line was also present on a new 1917 I had here later on.

The internal bore constriction was also not entirely unknown, but it was the first time I'd ever encountered it. For a while, I was an armorer for my PD and I worked on a bundle of the less expensive 64s that didn't get "premium gun" treatment at the factory, and I've been exposed to numerous Smiths since those days.

Agreed, rifling has not been 100% perfect in every gun S&W put out, but an overwhelming percentage of those guns had no bad rifling.
For those of us today who want to shoot lead, the chances are that, with 100% of the new guns using the new rifling process, 100% of those guns that we can buy new will not shoot lead as well as 99.9% of the older guns did.

The engraved drag lines I've seen on new Smiths came heavily engraved FROM THE FACTORY. It was due to the cylinder stop's sharp edge, an edge that was not there on older guns of my experience.
I have 30-year-old Smiths with a fair amount of wear that have a less pronounced groove engraved in their cylinders than the majority of the new Smith revolvers I've handled did right outa the box.

(In fairness, the new 686 sample I have here does not have that engraved line, due to the more rounded edge of the MIM cylinder stop they're now using, so I guess you could say that's at least one improvement provided by a MIM part. )

I have my old duty 25-5 with the notch burrs, I attribute those to rapid firing, not a cylinder stop, as such.

Stiffer triggers?
When S&W changed the internal geometry of the current actions to meet drop test requirements, the mainspring seat was re-located to provide more spring tension, to drive the shortened firing pin harder.

I consider just about any working revolver a "kit" gun, most of mine have had action work to lighten the triggers, so a discrepancy in trigger pull between makers and even between different models of the same gun is no issue for me. Even among the greatest sampling percentage of a given model the differences between trigger pulls would most likely not be an issue for most buyers, falling within a certain tolerance range.

The current Smiths can be problematical in doing action work, not just a matter of swapping for a lighter mainspring since that may result in light strike misfires. In such cases, replacing the short firing pin with a longer one has a better chance of success.
A new Smith with a quality action job (suitable for defensive use, not just competition) will most likely not be the equal of an older gun with a quality action job.

Broken firing pins have also occurred, but again- With 100% of the new Smith revolvers of K-Frame size & above using a shorter pin, you know you'll get that pin for certain (along with the drop-safe modifications that DO NOT improve the gun), whereas the percentage of broken pins on older models was probably less than 1%.
Even in new un-modified Smith revolvers, there are reports of misfires with some brands of ammunition that I attribute to that short pin. Such problems usually disappear when a longer pin's installed.

Forcing cones? Sure, there have been individual variances. There will ALWAYS be individual variances in a gun; you will still get 'em today, obviously, even with CNC equipment as cutting heads wear and tolerances stack. CNC & MIMs can't eliminate that entirely, and if a number of key areas that still require human QC inspection are ignored, as they were on those two bad 21s, the best automated processes now available along with the most precise MIM molds can't make up for what a skilled craftsman knew, did, checked, and cared about as he built a gun.

K-Frame magnums were never intended for much .357 use, as Jordan himself noted.
The guns developed problems because of the design envelope that the magnum pressures pushed too far. In .38 Special, most of those cones would last indefinitely.
I hardly consider that equal to a cone (or several) cut out-of-spec.
The first is a design issue, the second is a manufacturing issue.

Re the rest, yes, I said I do understand the economic exigencies of the current manufacturing/sales/market situation.
I'm not referring to a design issue, I'm not referring to a small sampling of older errant guns with QC issues, I'm referring to what i'm seeing personally in recent years vs what I've seen personally over 4 decades.
Yes, S&W put out the occasional lemon 50 years ago. Every maker did, has, does & will.
I've had two of Ruger's brand new .22 SP101s with bad cones (since corrected by Ruger), so S&W is hardly alone in the woods there.

But, from the Model 15 that my father carried as his duty revolver in the early 1960s on through my own exposure to military Smiths, police Smiths & my Smiths, I've had one 66 that needed the babbitt, and one 64 that needed a ratchet tooth corrected. The rest were fine; many were beat to hell, but they worked & the basic quality was there.

I've found far more QC annoyances in new Smiths in the past ten years than I did in the 30 years previous, and that tells me something.
In the past, I certainly had a chance of experiencing a failure or QC issue with an older gun, but today it's 100% certain I'll be getting features such as the rifling, the stiffer action, and the lock, if I buy a new Smith revolver above a J-Frame. None of those features do I consider "better" than what S&W was putting out 60 years ago.

On top of which, inspection points that should have been noted were quite obviously ignored in recent guns, and that bugs me more than the materials & design changes.

On the lock- It does activate itself.
Ayoob has documented it, Bane has documented it, it has occurred during a qualifier at a state agency here, and it is not an Internet "fable".
Mostly on J-Frames, yes, but it has been reported on larger frames, too.

On a toy, the lock can be ignored. On a defensive gun, I simply will not bet my life on it. It can be removed, leaving the side hole to plug (do-able), and also leaving a larger space between hammer and frame where the part used to be. That lets gunk in, which is a minor issue for most, but not for me when my guns are exposed to trail dust on an ATV.
Grinding the flag off leaves small parts inside that can still break or disrupt the mechanism when needed.

That lock can be dealt with, but I prefer to just avoid it entirely, and in no possible way can you persuade me that the lock is an improvement over the older lockless guns.

I genuinely do understand why S&W has chosen the route they've taken, and I do understand the need to evolve and survive. It's a tough market, and you either do what it takes to be competitive or you sink.
I have no desire to see such a grand old company name disappear from the firearms scene, and S&W isn't the only maker forced to adapt. Ruger's doing it, Taurus has, Colt has, and others have.
It's undeniably the wave of reality.

This new 686 does have a very tight lockup, no factory-induced drag line, no razor edge on the rear of the trigger to pinch my finger, a very smooth (but heavy) DA trigger, a crisp and repeatable 5.5-pound SA pull, and the overall machining is done well. It's better done than the last new Smiths I've had here.
I've not said they're junk, I've not said nobody should buy them, I just continue to feel that a good S&W sample today is not the equal of a good sample from 60 years back.

I do know why that is, I do understand the difference between the eras, I do not have to be happy about it.
Denis