How come Israel don't use Mossad to take out all of the Hamas leadership similar to what they did after Munich? Would this not be better than bombing stuff into oblivion?
Err... did I misunderstood the question, or do (nearly?) all commenters have no idea what they're talking about?
You're asking why Israel doesn't assassinate Hamas's top leaders, right? Or did I misunderstood and you asking Israel doesn't ONLY assassinate Hamas's top leaders? Or are you asking why Israel responded differently to Munich?
To answer the first question, well... they are. Hamas's top leaders according to BBC are:
Ismail Haniyeh - Killed.
Mohammed Deif - Probably killed.
Marwan Issa - Killed.
Mahmoud Zahar - Alive. is 79 years old and might not be active/influential in the leadership.
Khaled Meshaal - Alive.
Yahya Sinwar - Alive.
Also, keep in mind that the response to the Munich massacre took about 2 decades.
As to why Israel dosen't ONLY assassinate Hamas's leadership, the simple answer is that it won't solve anything. It won't bring the hostages home (It will probably have opposite effect as a. it will leave Israel without a centralized entity with whom to negotiate and b. Sinwar might be using hostages as human shields, which also might explain why he's still alive), and it will still leave Israel with a terrorist entity next door. The official Israeli version is that the assassinations, among other things, serve as leverage on Hamas leaders to secure a deal. Obviously, this is only effective if there is some leadership left.
If you're asking why Israel responded differently to Munich, it's because the situation is totally different in numerous ways. But the question itself is also factually wrong - Israel didn't only assassinate the leaders of Black September. Firstly, the goal was to "assassinate individuals they accused of being involved in the 1972 Munich massacre", not just the leaders. Not only that, Israel also responded with raids and bombings (for example: 1973 Israeli raid in Lebanon).
None of what's happening squares as a reasonable response. Munich is some horrible memory. Maybe someone else is obsessed with it, but the genocide occurring now is the concern.
OK, I'll just answer plainly, and if I misunderstood you, feel free to correct me:
OP asked about the difference in Israel's response to Munich and Gaza. I tried answering that to the best of my ability, as it seems most other answers didn't correct the implicit assumption that Israel doesn't go after Hamas's leaders. If you think someone is "obsessed with Munich", you should respond to the OP.
However, I get the feeling some people here took the question as "let's use this question to further convince ourselves/others that Israel is committing genocide in Gaza". In this context, your reply makes more sense when it's addressed to me.