And as is true in any military conflict, civilian casualties is a reality that unfortunately is unavoidable. In order to minimize it, the attacking force must put their troops in harm's way. But that's what they signed up for. No getting around that.
No collateral damage is the aim, it's just not the reality.
Exactly. At least ground troops have an opportunity to distinguish between a bunch of kids playing soccer on the beach and a grown man launching a rocket before pulling the trigger. And civilians can see or hear ground troops coming and try to get the hell out of the way. The IDF's leaflets are a pitiful substitute, particularly since they sometimes end up blowing up the exact same building the leaflets promised would be safe (like the UN school),
after people have followed the instructions to the letter. And also because when civilians evacuate their homes, the IDF regularly enters and trashes them.
The answer to the question of "how many civilian casualties are acceptable" is "as few as possible". The IDF is currently making almost
no meaningful effort to protect civilian lives, so ANY sincere effort would be a massive improvement.