>How are we supposed to win with no communication
You really aren't. Imagine a small scale RTS (DoW2) where each individual squad went off and did whatever the fuck it wanted and you only had control of one of those squads. That's DOTA and all other ASSFAGGOTS. Sounds like hell right?
Turns out, that if every one of those squads communicates and knows the intentions of the other squads without being prompted then it becomes a very rewarding and fun experience. Random players are unable to communicate effectively/quickly, they do not know your intentions. If you build up a team of friends (can even only be three of you) then you have effective communication and instinct of what eachother wants. Even better because you've got that critical mas of 3 people the other players are more likely to follow you.