In Leviticus 10:1-2, that's where the story of Nadab and Abihu is documented. They offered strange fire before the Lord but fire from the Lord burned them up.

If you read downwards, the Lord gave further instructions to Aaron through Moses about his holiness. One of those instructions is the prohibition of priests from taking alcohol before going into the tabernacle.

Then the Lord said to Aaron, [9] “You and your descendants must never drink wine or any other alcoholic drink before going into the Tabernacle. If you do, you will die. This is a permanent law for you, and it must be observed from generation to generation ( Leviticus 10:8-9 NLT)

Probably, Nadab and Abihu were high on alcohol before entering the tabernacle. That may be the reason they lost their sense of judgement by burning strange incense. This is a probability reading from the context of that chapter.

We may not understand fully why God decided to judge Nadab and Abihu but it is clear that God doesn't want us to tamper with what is holy. He want us to discern between the sacred and common.

What is common may not necessarily be sinful but what is sinful is common. Let me use the issue of bringing comedians to church as an example. I tell people that there is nothing wrong with comedy as a business or entertainment provided the jokes are not coarse. In functions like parties, one may invite a comedian to perform his art.

However, it is not a holy or sacred thing to bring a comedian to church to "entertain" God's people. In the church of the living God, we don't need entertainment, we need edification, instruction, correction and rebuke. That is the sacred purpose of the pulpit.

Apostle Paul says, "so that if I am delayed, you will know how people must conduct themselves in the household of God. This is the church of the living God, which is the pillar and foundation of the truth"( I Tim 3:15 NLT).

I am sure Paul will be surprised to see that our generation has turned the church( the pillar and foundation of truth) to a theatre of comedy. Why? We cannot discern between what is sacred and holy.  If Nadab and Abihu were judged for burning the wrong incense, what do you think will happen to anyone in that era who stand in the tabernacle to entertain God's people through comedy?
In some places, the painful thing is that the time for word ministration will be reduced to give room for comedians. These comedians will receive a huge honorarium for entertaining God's people but the guest preacher who fasted and prayed for the edification of the people will be dishonoured in his honorarium.

The manifest presence of God that is lacking in our meetings is the reason our generation is finding substitutes in entertainment.

Discerning what is sacred from the common seems to be so important to God. His expectation is that priests will teach it. One of the duties of priests is to teach between what is holy and what ia common.

Ezekiel 44:23 says,  They will teach my people the difference between what is holy and what is common, what is ceremonially clean and unclean.

Pray to discern what is sacred from what is common.