दोषैरेतैः कुलघ्नानां वर्णसङ्करकारकैः।उत्साद्यन्ते जातिधर्माः कुलधर्माश्च शाश्वताः॥
doṣair etaiḥ kula-ghnānāṃ varṇa-saṅkara-kārakaiḥutsādyante jāti-dharmāḥ kula-dharmāś ca śāśvatāḥ
Word by word
The verse says
By the misdeeds of those who destroy a family and cause this mixing, the ancient duties of community and household are wiped out.
In plain words
He repeats himself. The same claim as verse 40, tied off at the other end.
Community duties, household duties — both destroyed. He has been round this loop three times now in four verses.
Repetition was a sign of shock earlier in the chapter. Here it is a sign of an argument running out of road.
Where you've felt this · in creative work
A craftsman describes how nobody is being trained any more, and what will be lost when the last few stop. Every detail is accurate. It is also being said to avoid a harder conversation about what he himself is going to do next.
Going deeper
Something has gone missing from these verses, and once you see it you cannot unsee it.
Arjuna is no longer talking about anyone in particular. Verse 26 was fathers, grandfathers, teachers, uncles. Verse 34 was the same, in his own voice. Those were people. What he is discussing now is kula-dharma and jāti-dharma — the duties of household and community as abstractions.
His own family has been replaced by a theory of family.
This is what the poem is showing, and it does it without a word of comment. Grief reached for arguments, the arguments grew larger and more general, and somewhere in the growth the actual people dropped out. Arjuna started this speech unable to look at his grandfather's face. He is ending it discussing the collapse of social order.
When Krishna finally speaks, he brings it straight back to the particular: to Arjuna, to this body, to this action, to the thing in front of him.