If you think it being cooked (which it probably was, because it was a sacrifice) makes it less disturbing, then you haven’t gotten the point of the story

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Depends on what you mean by “understandable.” I find it very understandable that a zealous Jew would kill an apostate, as well as the royal official who was forcing Jews to commit idolatry. But perhaps we mean different things by the word.
Was it wrong in an absolute sense–contrary to natural law? I’m not sure it was. It is certainly not the way that followers of Jesus ought to respond to persecution. And obviously when Muslims today kill those they consider to be apostates (not that all Muslims condone this, but it’s mostly Muslims who practice it–Christians and Jews have pretty much abandoned the practice), we are horrified. But is it objectively wrong to kill an apostate? In practice, I certainly oppose it, because many “apostates” may be sincerely following their consciences, and the person in Maccabees was coerced by fear and not fully responsible for his actions.
But is deliberately abandoning the true God for idols intrinsically worthy of death? Yes, I think it probably is. We don’t advocate carrying out such a penalty today because we recognize that this crime, unlike others such as murder, depends in a peculiar manner on one’s intention, which cannot be discerned, and also because it has proven a horrible mistake in many ways for the Church to avail itself of the “temporal sword” to back up its spiritual discipline. But I wouldn’t describe either of these killings as the killings of innocent people, which is intrinsically wrong.
I am
far more bothered by the wholesale slaughter of men, women and children described in Joshua and 1 Samuel than I am by the violence of the Maccabees in response to brutal persecution by a pagan empire.
Edwin