cant imagine anyone spending out on decent kit and not having confidence that they will do the job they were bought for
The difficulty here is, one tends to generalise from the particular (my own experience, for example) to the general. You
know it's a fallacy to do so (or you should), but what
matters in a personal sense is one's own experience. My experience was that I bought "decent kit": Shim T105 in a ti-framed touring bike, and over ten-plus years, I had endless and apparently insoluble derailleur problems, esp with the rear der (this, despite changing about four drivetrains.) We don't need to detail the 'orrible details, nor their expense, because I've repressed everything. The 'orrible details did include a variety of Shim products, all considered good quality, if not top-of-the-range.
Suffice to say that, on a hot late-summer afternoon on loaded bike on a 10-plus% grade in the Madawaska Highlands, when my forever-out-of-adjustment-rear-der refused to, or couldn't, give me the low gear I wanted, I decided, "Sod it. Too much is enough. There has to be some other approach here."
Eventually, I found my way to a Rohloff, mated to a Thorn frame-and-fork-set, and in the three-plus years since, no matter the load or the gradient, I haven't had any moments of existential despair triggered by non-functioning gear mechanisms. I
have tested the Thorn-mit-Rohloff against the highest road passes in North America, and except for an unseemly mini-clank near the summit of Washington Pass (later traced to a loosening crank bolt) I didn't even think about my gears.
This is personal experience--I make no broader claims than that, and especially, no claims to general validity. The point, I guess, is that I don't much care about "general validity": in my experience, over a decade-plus with soi-disant "quality components", I had an endless stream of expensive and time-consuming headaches. With the Rohloff, I've had none at all. I've had a few problems with my Thorn bike, mostly linked to rims. These were not Thorn-specific, and none of them was debilitating or insoluble, or even very expensive. With the drive train, I've had no problems worth mentioning. I've made some tweaks in the ring/sprocket ratio, and in the Hebie chainglider, but the hub has been trouble-free. This history is wholly different from my experience with derailleurs.
I realize that my experience has been quite different from that of many other riders, and all I can say is that I wish that I'd had their experience...but I reckon that four drive trains from a reputable supplier over a decade-plus of cycling in three continents is a reasonable test, and I had reached the limits of my patience.
So Bill, whatever you may imagine, my practical experience is directly, comprehensively and expensively contrary. Wish it were otherwise, as I've suggested above, but as the song says, "Wishin' don't make it so."
Cheers, John