The merc analogy is interesting. I've had 3 cars in the last 30 years. All Volvo estates. I do a lot of miles. Ist 1990, 32k new. Second 2002, 32k new. Third 2008, 30k new. The last v70, before being discontinued was 27k for the same spec. Hang on, based on the 1st car the new one should now be 55k!
What's changed, well it's all thin plastic and steel that snaps / bends in the wind, the chassis and suspension is rubbish and wont see 100k and the interior is plastic and nasty.
The reasons its changed is the same as the declining quality of shimano parts in a parative groupset. Nobody would buy it if it was at a true inflationary cost. But by buying it you can still say "it's got shimano xt on it". Trading on the notion of past quality.
If I now ( or my company) spent 55k on a car it would (you hope) be better built than a 25k Volvo. But the 25k Volvo is still badged as the same model as the last 3 cars.
Same goes for your crank, spend 200 and get a great bit of kit, but DO NOT expect a budget xt " share holder friendly" product to be what is was 30 years ago.
Nothing is in terms of engineering and build quality at the same price as 30 years ago!