The losses outweigh the gains.
Arjuna begins to question the value of victory itself. He does not desire a kingdom, pleasure, or even life. If one must kill loved ones to achieve something, then it is no longer what he seeks.
Even if you achieve your goal, if you lose all the important people in the process, there will be no joy. Only mental suffering and torment will continue, both in this life and the next. Arjuna's question has shifted from "Can we win?" to "What is the purpose of winning?". This argument suggests that if the means are too terrible, even a kingdom or pleasure loses its value.
Japanese Translation from the Geeta Press Edition - Chapter 1, Section 32: "Not Seeking Victory, Kingdom, or Pleasure"
I do not desire victory, Krishna, nor a kingdom, nor pleasures. What is the use of a kingdom for us, Govinda? What is the use of wealth or life? || 32 ||
Vocabulary
"na kāṅkṣe" means "I do not want."
vijayam means "victory."
rājyam means "kingdom."
"sukhāni" means "pleasure" and "enjoyment."
"Govinda" is a name used to address Krishna, and in some annotations, it means "the one who protects the cows."
"kiṁ no rājyena" means "What use is the kingdom to us?"
"kiṁ bhogaiḥ jīvitena vā" means, "What is the use of pleasures, or even life itself?"
Translation
"Krishna, I do not desire victory."
I do not desire a kingdom, nor pleasure.
Govinda, What use is a kingdom to us?
What use is pleasure, or even life itself?
Annotated Translation
Arjuna faithfully depicted his own mental state.
He said that victory, a kingdom, and earthly pleasures obtained by killing those close to you and whom you love are not at all desirable for him.
He clearly saw it.
Killing those relatives will bring nothing but mental anguish and torment, neither in this world nor in the next.
Then, what is the purpose of fighting?
Why must we bring them to death?
How am I supposed to deal with a kingdom and pleasures obtained through such terrible means?
Arjuna clearly stated that things like their lives after he killed them would be of no use to him.