فَإِنْ كَثُرَ الْقَوْلُ وَقَلَّ النَّفْعُ، فَبِمَ نَفْتَخِرُ؟
If talk is plentiful and benefit slight, what have we to boast about?
The conditional sets up a case in which talk is abundant but benefit is small. The following question is not a request for a list of things to celebrate; it challenges the grounds for pride.
The passage does not say that extensive speech is invariably pointless. It challenges the imbalance between abundant claims and negligible results.