I found it hard in the beginning of my journey into Hinduism to accept that animal sacrifices was once the mainstream practice of early Hinduism. At the time I was a vegetarian and animal lover, so the idea was repugnant to me. So I rationalised it by accepting the Arya Samaaj interpretations, where they literally torture the Nirukta(Vedic etymology of Yaksha) to prove that cow does now mean cow, goat does not mean goat, horse does not mean horse e.g. sanskrit for goat sacrifice is 'aja medha' and if you break down the sandhi to a+ja it can rendered as unborn. Medha is translated as sacrifice, but if you torture the sandhi, it can be rendered as wisdom --- hence it becomes sacrifice for wisdom of the unborn. They did the same with ashva+medha, which can be broken down as ashva meaning swift and fast and medha, again sacrifice or wisdom, so you get sacrifice for the swift and fast, or for power.(It was indeed a sacrifice done only by kings) The most ridiculous break downs were of the word mitra, broken down mi+tra, meaning the smallest measured one, rendered as hydrogen.
It took a while for me to gain enough to maturity to accept that the early brahmanical religion was indeed a sacrificial religion, and if it wasn't, then why would it have come under extreme criticism by the Shramana movement of the Jains, Buddhists and yogis, and why would animal sacrifices still exist in some sects of Hinduism today. As my knowledge of religion grew, I realised that animal sacrifice in that day and age was in vogue all over the planet, it was a mark of its time, it was practised in Babylonia, Egypt, Judea and by the time we transitioned into the age of philosophy, dubbed the axial age, it started disappearing all over the planet. The later Hinduism of Vedanta moves to more lofty and sophisticated concepts like ahimsa. Just as it would be unfair to criticise Christianity because of the OT, it is unfair to criticise Hinduism because of purva-mimamsa.