Whoever considers Torah and Injeel as his/her main source of guidance can be considered as Ahlul Kitab regardless of their deviance and shirk. All their denominations and sects are also considered Ahlul Kitab as long as their source of guidance is Bible or Torah.
People of the Book consist of both believers and disbelievers.
The scholars allow marrying their chaste women and eating their slaughtered meat even today.
We do not discriminate between them based on their level of deviance. There might be believers among them and also, disbelievers.
Allay says (interpretation of meaning):
"O people of the Scripture!: Why do you disbelieve in the verses
[about Prophet Mohammad (peace be upon him)] of Allaah, while you
(yourselves) bear witness (to their truth)". (Aala Imraan, 3:70)
"Say: O people of the Scripture! Why do you stop those who believe
from the path of Allah, seeking to make it crooked, while you
(yourselves) are witnesses? And Allaah is not unaware of what you do".
(Aala Imran, 3:99)
and also, Allah mentions about believers among them who worship Allah and also, believe in our Prophet (salallahu alayhi wassalam) and the Qur'an which was revealed to him
Allah says (interpretation of the meaning):
"Not all of them are alike; a party of the people of the Scripture
stand for the right, they recite the Verses of Allaah during the hours
of the night, prostrating themselves in prayer. They believe in Allaah
and the Last Day; they enjoin what is right and forbid evil and they
hasten in good works; and they are among the righteous. And whatever
good they do, nothing will be rejected of them; for Allaah knows well
those who are the pious". (Aala Imran, 3:113-115)
"And there are, certainly, among the people of the Scripture, those
who believe in Allah and in that which has been revealed to you, and
in that which has been revealed to them, humbling themselves before
Allah. They do not sell the Verses of Allah for a little price, for
then is a reward their Lord. Surely, Allah is Swift in account". (Aal