Why are books on Creed written prior to Ibn Taymiyyah not taught, with only his works and the works of his students being deemed sufficient?

The Ahl al-Sunnah (Sunnis) rely on the Qur'an, the Sunnah, and the consensus of the early Muslims (Salaf) for establishing their doctrines. They also rely on concise, later texts due to their simple language and the abundance of issues they address, as is customary for scholars in all fields and schools of thought.

Their reliance on the works of Ibn Taymiyyah or Muhammad ibn Abd al-Wahhab is not unusual, as it is a common practice across different madhhabs (schools of thought).

There are many old Salafi and Athari (traditionalist) creedal books such as "Al-Iman" by Abu Ubayd al-Qasim ibn Sallam, and "Usul al-Sunnah" by Imam Ahmad.

As for Fiqh (Islamic jurisprudence), its widely circulated books are numerous, and the Salafi Hanbali shaykhs do not limit themselves solely to the preferred rulings of Shaykh al-Islam Ibn Taymiyyah.

This reliance on certain concise texts has its reasons related to teaching, and it does not constitute a turning away from the books of the early Muslims (Salaf); rather, the advanced Salafi texts should be read.