Well, I think the Syrian situation is a mess and any solution is far from ideal. If you go against Assad, there will be endless civil wars and some Islamic faction will take place in power but supporting Assad against the Islamists, you really are playing right into Russia and Iran's hands.
Can't blockade them, guess you could go in there and assassinate Assad but then whoever replaces him is going to end up being a jackboot too, else the country will collapse altogether.
I wonder if Trump's actions weren't a signal to North Korea and China not to yank his chain but he did do a 180 ("evolving"). Don't want ISIS to have territorial state over there, don't want a failed state next to Iraq, don't want a gadzillion more refugees flooding Europe, don't wait to reinforce Putin and Iran's stranglehold in the region, if we intervene, need a clear concept to where it could lead to.