Is it permissible to delay ghusl for days after intercourse without an excuse, given the lack of commitment to prayer, and is the person considered najis (impure) or in a state of impurity during this period?

We have previously issued a fatwa regarding the ruling on delaying ghusl (ritual bath) after janabah (state of ritual impurity) under number: 72846. The five daily prayers are a pillar of Islam, and their validity depends on purity from both major and minor ritual impurity. It is not permissible to delay ghusl for several days. Deliberately abandoning prayer without a valid excuse is a major sin that many jurists consider to be akin to major disbelief (kufr akbar) which expels one from the fold of Islam. Deliberately missing even one prayer until its time expires is a greater sin than adultery, theft, drinking alcohol, or murder. Ibn al-Qayyim transmitted this consensus at the beginning of his book "Kitab al-Salah."

It does not matter whether a person is considered ritually impure or not if they abandon prayer. The matter is serious and entails many rulings in this world, and disgrace in the Hereafter if the person dies persistent in abandoning prayer.