I think a basic problem with your analysis is that there will always be an emotionally compelling reason to commit troops to enterprises like this. We have to support our allies, the Kurds. Saddam Hussein and his sons are cruel dictators. Iranian theocrats are intent on destroying Israel. There are concentration camps in North Korea. Gaddafi is a dictator and sponsor of terrorists. Etcetera.

These reasons aren't wrong, those things are true. The problem is that they lead down a path of interventionism which hasn't worked very well. For example, Iraq. Hussein really was a cruel dictator but by invading and destabilizing the region the conflict killed a million or more people, generated ISIS, and left the area tumultuous.

I also want good things for the people of Syria. I don't think it's fair for them to be ruled by Asad. Where I disagree with people who advocate continued military intervention is that I don't think this is the right way to help them.

I think the right way to help people is by exemplifying the virtues of our system of governance and economics. We should become a country that others want to emulate. We should spread good ideas, like the rule of law, human and civil rights, regulated but mostly free markets, etc. Other countries will desire our prosperity and change of their own accord to become more like us, not because we're pointing guns at them, but because they genuinely want to live the way we've shown is possible.

I see this approach as unraveling the networks of evil in the world. Russia changing to be less of an oligarchy, permit more free press, better cooperation with the world, more Democratic will likely entail less support of Assad.