Anyone faking an injury on my pitch used to get a red card for conduct detrimental to the game. So I consider 5 minutes to be very generous. I'm aware that it's quite a long time. That's the point. Provide a disincentive.
You cite the example of quickly throwing the ball back in. Yet average high school matches get a replacement ball to the thrower quicker than at the World Cup. Worse, everyone seems to be OK with having the thrower creep down the field for 10 yards until throwing it with all kinds of crazy side spin on it.
To most of us, you seem like the abused who now sympathizes with the abuser. You want egregious human error unjustly changing match outcomes? You want to continue to foster an ethic of diving and unsportsmanship?
To reduce this aspect of the game, you've got to provide disincentives. The key is to pick disincentives that do not change the fundamental "flow" of the sport. It's really very simple. I expect that at some point in the next 50 years, there will be some leagues that tinker with the rules, become immensely popular, and people will forget the current dark ages of corruption, incompetence, and unsportsmanlike, disgraceful on-pitch behavior.