As with Chapter 21, priests need to live under strict conditions in order to be able to minister between God and man.
Offerings need to the be the firstborn, without blemish, for it to be acceptable. The conditions and the process needs to be perfect as well. Is God being unreasonable? Perhaps. But because of God’s perfect nature, this is the only way.
Clean and unclean – this is clear from the beginning. You cannot make an unclean thing clean by adding something clean to it. On the other hand, a clean thing becomes unclean when something unclean is added to it. Same with perfect and imperfect. Perfect + Imperfect is Imperfect.
To make something clean, there needs to be a sacrifice of blood from a clean thing. And 2000 years ago, the ultimate sacrifice as made.