Everything you say is true, basically. I just don't know how technical changes would change or maybe even ruin the flow of the game. I would NOT want the game to be stopped for the ref to walk over to the sideline and have a look at a TV.
I often catch myself thinking about some kind of laser-based device that can recognize offsides and maybe blow a loud honk or something, or something similar for the goal line. But yeah, maybe it's time. It's been a bit much this WC.