There have been actual independent autospies done, I don't mean a quick glance at a body. And I would build tunnels too if my neighbor had a history of bombing me and seizing my terrority.
Every non-state militant group is claimed to use the civilian population as human shields. This simply isn't true, it's rhetoric to justify the bombing because it's simpler than fighting on the ground. In assymetric warfare a resistance group has no choice but to be active in the place they are stuck at. Even if they were using human shields, it shows the IDF is heartless because they have no concern for any civilian deaths, including Israeli hostages.
It's like if a bank robber took a hostage and a cop just blasted through them, killing half the bank. That would be horrific and unnecessary murder.
If Hamas wasn't there, an even more effective group would emerge to fight Israel. The offensive on Oct 7th was by a coalition of groups. You say no one made Gaza put them in charge, but Israel has spent millions propping up Hamas. They were chosen by Israel specifically because of their unpalatable extremism. Israel has supported Hamas materially while taking steps to thwart other groups. Israel has used all avenues possible for years to create the situation we see now.