I don't disagree with your posts greater point, but I disagree with this.
There is an endless amount of variable complexity in the engineering behind friction materials, actuation styles, the control systems within the computer control, the material selections.. the list goes on.
I mean entire branches of metallurgy were more or less founded in the pursuit of finding stronger alloys for gearbox work. entire branches of metrology were developed for the sake of gearbox failure analysis -- there is a lot of complexity.
It's stupid to get into a pissing contest between engines and transmissions, they're both astoundingly complex.
A clutch-and-planetary hydraulic transmission is just a series of the same basic gear set design. That gear set may be made of exotic materials but once you have one the rest are basically identical. Combining them is only a question of packaging, control, and manufacturing tolerance. All complex on their own but equally important to an ICE.
The linked AA80E from 2007 is an 8 speed. 10 speed designs are not much different.
They’re all fundamentally the same selectively lockable series of gearsets we have had for the better part of a century.
Modern ICE are also extremely complex. Turbo systems, sensors, air management, heat management, the list goes on.
So yeah, a modern transmission is complex but a modern ICE isn’t simple. By comparison they’re very similar in terms of complexity, the ICE possibly being even more complex.