I consider indulge “do something which is kind of desirable, cool, but not the best in terms of effectiveness”, “do something which is a luxury”
Maybe, it’s like in a phrase in a criminal film: “I got more motivation to kill Bill than either of you, he is a luxury. Our problem is to hit the bank or split right now...” I would rephrase the first sentence as “We can’t indulge to kill Bill” in the said concept