When did you become the ultimate arbiter for what is good for baseball? Marathon games aren't good for players, management or broadcasters, so what are we really losing if they cease to exist?
What is so great about marathon extra innings games that they need to be preserved? Do you like watching position players pitch or something? Like it or not the game has been changing and it's becoming far more difficult for teams to cover the extra innings that these games entail. Management wouldn't like these games as it completely blows up a bullpen and it would be harder to work around due to the limit on player options. Players only end up with higher chance of injury due to fatigue and further disrupted sleep schedules. Nobody really stands to gain anything from marathon games so it makes sense to do something to attain a result in a more reasonable timeframe.
I'll agree the ghost runner idea is a bit gimmicky but this is nowhere as bad as something like a shootout. The same basic rules of the game still apply, there are still the same number of fielders, the same battle between pitcher and batter occurs, there are 3 outs per side, home team bats last etc.