Is destroying access points enough?
Temporarily it is. At least that is my thinking. It seems that Israel is engaged in siege warfare. They have Gaza split into two and the north is completely cordoned. No fuel, food or water is reaching Hamas in the north. They are under bombardment and shelling 24/7, while IDF soldiers can rotate between the war zone and peace and quiet to eat and sleep.
Hamas terrorists with either die of kinetic force or dehydration/starvation. When they are dead the IDF can finish destroying tunnels at their leisure.
No, closing a tunnel access is not enough in the long run but if they took out 20-30 feet of the tunnel and put a seismometer then they can covered their back for behind the line attacks. They an come back later and permanently collapse the tunnel at their pleasure.