re: Train multiple CNNs on different things
The problem is that it's not training in sense of an animal or child. It's really a method of storing data compressed from human selected / tagged images. The non-texture, shape based approach is really hard. Actually it's so far an unsolved problem.
A chair is good example. If not mostly based on 'texture' in loosest sense, then you need images not just of every sort of chair but almost every angle.
A child understands "chair-ness". The child can even decide if a box or rock or lap can be used as a chair.
So called "AI" or Neural nets have no abstraction at all, no intelligence*, they need specific examples. They don't "recognise" but match.
* Actually no-one has come up with a useful definition of intelligence, except in very general terms of tool using and problem solving in situations never encountered. Certainly not one that can be converted to an algorithm. Perhaps the best that can be said is that we can recognise it. Untrained people can easily be taken in. Eliza version of Turing test, which was never a serious proposal to test AI, but to test people. IQ tests don't test intelligence, even the guy that invented them said so, though the USA Army, and HR depts like them.
By late 1960s it was obvious what Turing had suspected in late 1940s and Lovelace in Victorian era. Computers could flawlessly do very difficult things, that even an expert human would make mistakes at. Yet would probably never master apparently simple things a five year old child, or even a rook or chimp does easily. It was dubbed the AI paradox.
See also https://en.wikipedia.org/wiki/Polanyi%E2%80%99s_paradox
Also it's true, though people seeking grants, investment and to sell their solution won't admit it: ""Every time we figure out a piece of it, it [AI] stops being magical; we say, 'Oh, that's just a computation.'"
Neal Stephenson tries to examine this in "The Diamond Age: or A Young Lady's Illustrated Primer"
Spoiler: The nanotech stuff and some other aspects are really magic & fantasy rather than SF, but an entertaining book.