Even 100 players would not require a single megabit of bandwidth. Games are not that bandwidth heavy. The overhead is in the lag of sending and receiving a lot of data.
I understand why they made it work like this better than you do. Don't parrot propaganda and slogans you don't understand. This applies to all areas of life by the way. And there wouldn't be much of a difference making it system wide because you'd maybe see 10 or 15 players instead of 4 or 5. If an instance approaches the player limit such as in the case of community goals and whatnot, then just make more instances. Not hard.
Why do you post? Just stop.
OMG How rude, just because I don't agree LOL, your method just wouldn't scale right ...