2) Webcam isn't strictly necessary: You'll be able to "see" your teacher, type in chat, virtually raise your hand, etc.
3) This enables more advanced STEM (The "T" portion, really) not because it's a desktop but because of the built-in 40-pin connector opening it up to the massive catalog of projects that exist for the Pi platform already.
4) Perfect is the enemy of the good: You're complaining this isn't a perfect solution for those lacking resources. It's not. But it is significantly better than nothing, or a phone with a 5" screen and no keyboard.