So it's likely that most eco-systems which rely on competition will crash. Every so often you'll get a planet that makes it through, but it won't be a common happening.

That's no proof at all. You still read about the Zeno's paradoxs, yet they are no paradox whatsoever.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi

Egoistic resource exploitation could be as easily positive as negative, because less resources are wasted on everyday living of many people. Arms races can help technological development. Slave labour can help to do things which people don't see as important enough to engage themselves.
More effective than competing nations could be of course a plutocracy, which eliminates most old, useless  or disabled people, sucks all resources normal people don't need to survive into their pet projects, and has no scruples to send people on deadly risky missions for their entertainment.

Der Amerikaner ist die Orchidee unter den Menschen
Volker Pispers

or because there's a quarantine on emerging civilizations.

Isn't that the Star Trek philosophy?

On a rational level, I'd find it supremely arrogant (or a cosmic comedy) to have humanity as the first species at least pondering on interstellar travel...

Yet on interstellar travel, I always get stuck in the quandary of transportation and time. Rumsfeldian "we don't know what we don't know" may offer a pinch of hope, but for a while now I've been leaning to the idea that intelligent life, even if has flowered copiously through the galaxy, is hopelessly stuck, each on their own gyrating piece of rock, each and every one feeling miserably alone. And in space, as the saying goes, no one hears you scream.

And that's what I'd call tragedy.

The former are obviously unlikely, in any form we would recognize.  

The latter assume they still use radio as a means of communication, using inefficient, simple codes.  Again, if they are using radio at all, the search for information efficiency has already lead them to formats that sound to outsiders like noise.  Guess what:  The universe is full of radio noise.  

Assuming they use radio at all.  But would they?  Not if they had something better.  What would THAT be?  Well, perforce we would have no clue--as should be obvious.  

The biggest problem, though, is that we imagine them to be like us.  But if they are, they have already crashed and burned, leaving no interstellar trace but a century of rapidly fading radio modulations--which no one (being either too primitive or having already crashed) has the sensitivity to catch.  

The Fates are kind.