Hamas claims to have launched 5000, but other sources say 2000 unguided rockets. There was no way to stop that many, which is why they launched all at once. They knew it would overpower the defense system.
They use a combination of a couple of tactics to overwhelm the enemy, apart from the launching of large number of projectiles, drones are also used to hunt down the defense batteries and radars directly and at the same time a large scale cyber attack is perform against the entire cyber infrastructure of the Zionist regime that includes the air defense (radars, Iron Dome, David's sling, etc) to disable or disrupt them.
Gone are the days that all Palestinians had against the heavily armored enemies were stones.