I think they're being reactionary to appease public opinion rather than dealing with the issue logically.
You're a good case in point. Corbyn discusses the problems, but you've attacked him for being 'out of his depth' for not having a decisive action plan.
It's better, apparently, in politics to be seen doing something, even if in 2 years time its shown to be demonstrably wrong, for the sake of being seen to do something.
It's more complicated than that.
When IS invaded Iraq, I thought the best thing the West could do was nothing. A long, costly American and British intervention had just ended with an outcome which hardly advanced Western interests, and there was little to be gained by running back into the swamp. IS's energies were focused on the establishment of its regional Caliphate, and the idea, advanced by some politicians, that its sympathizers were traveling from Western countries to fight, and perhaps die, in the Middle East, merely to use the newly won territory as a springboard to attack their countries of origin in Europe, didn't make a lot of sense. So stay out, stay neutral, don't make another war in a faraway land the West's war, seemed the best response.
But, for me, all that ended with the plight of the Yazidi refugees on the mountains in Sinjar. How to stand by and watch IS massacre innocent people when we could do something about it? The murderous barbarism of IS proved impossible to ignore. Predictably, once air strikes for 'humanitarian reasons' had taken place, the line rapidly dissolved, and soon the US was fighting a fully fledged air war.
The question is where the line could have been drawn? Because of the nature of IS, a victory for them would have had appalling consequences for the people of the region. Would it really have been possible for the West to do nothing?