"Take over" is hindsight. The MB was just a part of the rebel groups we were supporting, not our favorite part, but a deal with the devil.
You would have kept our troops there, increased them?
Several senior military officers thought they were nobodies, and in light of "no man left behind", the deal was widely supported by the men in charge.
The russkies also supported the position and urged Assad to cooperate and destroy his chem weapons, which he did, ahead of the schedule imposed by watchdogs.
More sanctions, or war with Russia?
No one believes this position. Certainly not the experts.
With Saddam out and the US troop pullout, which the American public supported, it is hard to imagine ISIS would not have risen.
Leaving the armchair generalship aside, in all seriousness, and as I am presently reading a history of the Roman Empire, whose deeds included repeated invasions of the ME all the way to Persia, (and interestingly, the almost complete genocide of Jews in Palestine under one emperor), and also considering that conflict if not open warfare in the ME has been in the news at least since I came of age, I don't think Obama has been much worse. Sure, in hindsight, he could have done better. No president has succeeded in bringing peace to that region, though many have tried. What's new with Obama is that he has a particularly zealous number of haters, and factoring out all the "terrible" things he's done which most other presidents have done as well, there is really only one remaining, unspoken, trait of his which explains that hate.