Spiritual practices change over time. Human beings are no longer murdered as sacrifices upon altars so much as they used to be. Neither are animals. Beliefs are also vastly different today than they were a thousand years ago. Spiritual practice changes through Time, because beliefs change through Time - with experience, our knowledge and wisdom increases, our understanding of belief improves. Though there are those who would criticize the inconstancy, it is nevertheless proper that spiritual practices reflect belief, and belief change with experience - for otherwise, those spiritual practices by which we gain experience sufficient to explore our beliefs are for nothing. It is for the purpose of such change and growth we practice.
Consider in your own life how your practice has changed, how your beliefs have changed. How we may improve our practice and belief; how society's beliefs and practices must change. Would we continue today in that primitive practice of human sacrifice, spilling the blood of one who offended that Blind Goddess, Justice? Has enough blood been spilled for us to see that the blood of victim and criminal are mixed, even a Goddess cannot tell them apart? There has been enough blood to give pause to our practice; it is to be hoped that there will arise a moment of hesitation sufficient to comprehend the necessity of self-restraint. And this will give rise to the humility of self-doubt. And that will lead to a doubt in the way we worship Justice - and other gods.
A belief requires an apprehension of truth, and this apprehension would require a valuation of that truth, that one belief is valuable, and another is worthless. Knowledge is a belief, seeing is a belief, hearing is a belief, touching is a belief. Believe only that there are beliefs. These beliefs are taken up, held, obsessed upon. Believe that having been taken up, beliefs are then held. Having been held, beliefs are obsessed upon. Believe that the ignorance of truth creates a desire for belief, and this causes a hatred of what is contrary to that belief. Believe that beliefs cause suffering. But also that beliefs can - and will - be let go and uprooted.