I really think there are two different aspects to the classification of the threat. It’s actually pretty analogous to the Afghanistan War.
First, neither Al Quaeda nor Hamas represent an existential threat to their opponents. The US hasn’t really faced a believable existential threat since the collapse of the USSR, Israel hasn’t really faced one since the 80s. Countries in Eastern Europe face an existential threat from Russia. And so on. Killing 1200 (or 3000) people, no matter how brutally or unjustified or evil it seems, it does not threaten to destroy the state of Israel. It is, of course, now an existential threat to Netanyahu, which is one reason why it’s being pursued with such enthusiasm.
The second aspect builds from the first and questions whether the solution pursued by Israel (and the US) were both efficient (ie proportional to the threat so as not to divert attention and resources from other threats) and effective. They have to be expected to achieve specific and measurable goals and timelines.
The ability to pull off an Oct 7th might have been equally well but more efficiently and effectively with intelligence and commando units, and Israel would have been given free rein by most of the planet to do so.