There were two major revivals in the OT, with Hezekiah and Josiah, that were both marked by a reinstitution of the Passover Festival. The one by Hezekiah was considered to be the greatest one since the the time of Solomon. However, the one by Josiah, about 100 years later was considered to be the greatest one since the time of the judges. I have an opinion on why Josiah's was considered deeper and more meaningful and I think it relates directly to today's generation:
I. Hezekiah's Revival / Passover
II Chronicles 30: 2 "The king and his officials and the whole assembly in Jerusalem decided to celebrate the Passover in the second month."
II Chronicles 30: 18 - 20 "Although most of the many people who came from Ephraim, Manasseh, Issachar and Zebulun had not purified themselves, yet they ate the Passover, contrary to what was written. But Hezekiah prayed for them, saying, “May the LORD, who is good, pardon everyone who sets their heart on seeking God—the LORD, the God of their ancestors—even if they are not clean according to the rules of the sanctuary.” And the LORD heard Hezekiah and healed the people."
Hezekiah had a passion for God that was driving him and the people to celebrate, whether they got every aspect of it right or not. They celebrated it in the second month, a month later than prescribed, because they couldn't get it ready in time. They allowed "unclean" people to participate for the same reason. They just wanted to have the celebration and the rules were somewhat cast aside because of their passion.
Hezekiah understood this and prayed to God that it would be okay, that in this particular moment they could bend the rules a bit - and God allowed it. God, in a sense, sidestepped His own stipulations of the Passover to allow the people to celebrate because He knew the intention of their heart, and He healed them.
II. Josiah's Revival / Passover
II Kings 23: 21 - 23 "The king gave this order to all the people: “Celebrate the Passover to the LORD your God, as it is written in this Book of the Covenant.” Neither in the days of the judges who led Israel nor in the days of the kings of Israel and the kings of Judah had any such Passover been observed. But in the eighteenth year of King Josiah, this Passover was celebrated to the LORD in Jerusalem."
Josiah had found the Law buried in the rubble and idolatrous pornography that that had filled the Temple, and had thus proceeded to "clean house." Everything that was not of God was smashed and burned and scattered over the dump site outside the city. They were going to get it right, because they had the Word. When they celebrated the Passover, they did it according to the Word of God. They got it right.
Josiah's revival and Passover celebration leapfrogged the acclaim of Hezekiah's because it combined the passion with the truth of God's Word. There is a reason God prescribes things a certain way - because it is under this prescription that we are able to fully find the joy and power that He is offering to His people.
So why is this so important in today's generation? I believe that we have young people who are on fire, who are returning to the Lord, who want to be in Him, who have a passion for celebration and revival, and who want to get into the lives of others with the message of Christ. However, in their passion the Word of the Lord is in some ways being set aside, or not embraced to the level of fullness that it demands. If this is left unchecked, this passion will either burn in the wrong direction or it will burn out. It will be a useless fire.
I fully believe that as God allowed the people of Hezekiah's day some wiggle room to celebrate apart from every "jot and tittle," we must embrace this generation and give them the same slack as they enter into their own celebrations. But we also must continually direct them and disciple them into the truths of His Word so that they will experience the fullness and the power that God desires for them.
II Kings 23:25 "Neither before nor after Josiah was there a king like him who turned to the LORD as he did—with all his heart and with all his soul and with all his strength, in accordance with all the Law of Moses."
Josiah had an intense passion for God that burned to the depth of his soul. What made it so effective and cleansing was that it was fully aligned with the Word of God.