I think the consequences don't match the action, if we assume that RCs are being handed out for foul or dangerous play.
Here's an NRL example.
Broncs/Panthers Thursday. The Broncs star full back got a head to head contact. In any sane universe, it's a red card - in this one, it's on report.
Walsh went off and stayed off. Panthers player stayed on. The cynic in me still thinks Walsh was targeted.
So, all Ian's use case parameters are met - we still have ful teams playing each other.
Game was ruined, as so much of the Broncs offence and defence organization runs through Walsh.
The outcome did not match the action. And that's what 20 minute red cards do; they minimize the impact of acts of foul or dangerous play. If you don't want the game "ruined" - which is a hyperbolic way of looking at it - get coaches and players to do their bit and adapt.