Some boutique oils are superior in several ways to the mainstream stuff found at Wal-Mart. The question becomes- does it need to be superior? What is the goal?
Most engines can last ~250K miles on a cost efficient oil found at WM that meets the OE requirements for the vehicle. Most cars will be 20-30 years old at this milage and be pretty well trashed otherwise, so there's not much point in trying to get more miles out of the engine. At this point the plastics are brittle, the interior is crumbling, the door seals are all falling off, the various exterior trims are flaking, the paint is peeling, rust is creeping in, the engine bay is full of dry rotted hoses and tubes ready to spring a leak if you look at them cross-eyed. At this point, most cars are ready to be retired to the recyclers. My Wife's car is 18 years old with "only" 146K miles on it. At the rate she accumulates miles the car will probably have about 225K miles on it when the car is 30 years old. I doubt we'll keep it that long... But the point is that, I don't need a fluid in this car to get it to a 350K mile finish line.
Now... if you have different plans for a car, like putting 25-50K miles per year on the vehicle in some sort of driving job, then suddenly, the wear and tear of the engine and driveline are going to take place at a much faster rate than the general rotting of the rest of the vehicle from the passage of time and exposure to sun/elements. In this case, it may be desirable to use fluids throughout the driveline that provide greater protection from wear and deposits, in an effort to extend the usable life of the engine to 350-500K miles. I would warn that there are some engines and transmissions that will fail much sooner for reasons that no oil can solve, so this is sort of a gamble.
Another example where "boutique" makes sense to me is for the purpose of extending drain intervals on transmissions, transfer cases, t-cases, and diffs, or to attempt to get some of these components to last to the ~200-250K finish line where they are known not to with ordinary maintenance (or no maintenance, as is often the case with "lifetime fluid" recommendations these days). Fluids changes in transmissions, t-cases, and diffs are generally more difficult than changing engine oil, so a more expensive fluid that can extend the interval pays for itself in convenience. I would also argue that a boutique oil may offer a way to "make up" for the excessive wear from "lifetime fills" used longer than they should have been in these systems. Like, you buy a used car with 100K miles on it, with the "lifetime fill" fluid still in the transmission. If you leave that fluid in there, it will last till 150K miles. If you change the fluid at 100K with "normal" fluid, then again at 150K, it will probably last till 200K, but if you swapped it out for boutique oil instead at this juncture, and change it "as needed" thereafter, (it will probably last longer than regular oil), then the transmission might last till 250K+ instead. So in this case, the fancy fluid might be "buying" an extra 50K miles by stalling the wear-and-tear of the transmission. YMMV...
