Bombing supports Daeshs propaganda that the west are cowards and without an appropriate follow-through/withdrawl plan this idea will flourish and find new support in the middle east.
It would be better for the Syrian people if we let Assad lead the fight and offer him lots of support. The Syrian people would prefer Assad restoring order to being bombed.
The UK Foreign Affairs Committee published a report saying there should be no British airstrikes in Syria without a coherent international strategy to both defeat ISIL and end the Syrian civil war.