I think it depends on your view on expected life of a tranny.

If you're ok with an avg BMW x5 auto tranny 'failing' every 100-150k miles for 4-5k in repairs, then I think the modern transmissions are up to snuff

If you're looking for 150-200K+ miles, then you will disappointed.

Modern cars are designed for early obsolescence. Most new car owners don't keep their cars for more than 6 years. Car companies and parts makers recognize this and look to capitalize on it by making long-term ownership more painful (encouraging you to trade-in and up)

Most car companies are racing to the bottom in this regard whether it be window regulators, trannies or other components.

Maybe a longer powertrain warranty is in order but I'm guessing BMW is able to skin the cat more closely by doing the business the way it is. Some complain, some never buy a BMW again but enough come back for another to make it worth their while.

I would love BMW to make its cars lighter with less electronic gizmos but I know that is not the common buyer viewpoint anymore.