Those who perpetuate it
Specifically refers to those who perpetuate it i.e., the religious leaders who lead the people to follow these matters such as naming the Angels with female names.
إِنَّ الَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ لَيُسَمُّونَ الْمَلَائِكَةَ تَسْمِيَةَ الْأُنثَىٰ
“No doubt, those who do not believe in the hereafter name the Angels with feminine (or female) names”.
Contrast with the previous verse
إِنْ هِيَ إِلَّا أَسْمَاءٌ سَمَّيْتُمُوهَا
“They are nothing but names that you have made up”
It is argued that the difference between this verse and the previous verse is that the previous was general in relation to the origin of the Shirk (i.e., the association with Allah and invention of their Gods and names), whilst this Aayah is about an action that is continuing to be undertaken and specifically refers to those who perpetuate it i.e., the religious leaders who lead the people to follow these matters such as naming the Angels with female names.
Continuing action and its agents
Discrediting their claim
The statement that they don’t believe in the hereafter is to discredit them and reveal that they are really “conmen” who have no real belief.
Strong rebuke and implication
It is also a strong rebuke for their naming Angels with female names implying: How can you dare to invent matters about the Angels (the very Angels whose great power has already been mentioned in the Makkan verses).