What the IDF may be able to do, ultimately, is to kill a significant % of Hamas fighters and those to cowardly for even that, and destroy Hamas' stockpiles of weapons, and take control of egress and exit from the Gaza Strip, which would include imploding tunnels from Egypt.They are human shields because of how the city and tunnels are built. I don't think it's possible to wipe them all out, and there is no way they can wipe out a substantial portion of Hamas without a civilian death toll in the tens of thousands at least. Plus bombing might not affect the tunnels. A million people is impossible to move fast, especially considering there are old and handicapped people.
Hamas probably has tunnels in other places in Gaza as well.