But worth saying that Israel's government thinks it can achieve the goal of destroying Hamas, and even if not, it is possible that when the war was launched, it did think it could be achieved (and e.g. underestimated Hamas).

Also, we use "achievable" here as if it's one dimensional, but it's not - the question is actually "achievable at what cost", where the cost is in Palestinian civilian lives lost and the population displaced, in IDF soldier's lives, and in disruption of the Israeli economy.