'The Bible also isn't just one book, it's a collection of (sacred) texts, by multiple authors in various places, spanning thousands of years.'
The texts are only sacred if you have taken the leap of faith required to believe that they are. To me, they are no more and no less sacred than any other texts, and the things Terry Pratchett talks about resonate with me a great deal more than much of the Bible. You have but to read the Vimes series to realise the man had an excellent moral compass.
Sin is a meaningless concept, since it includes things that are only 'wrong' because some people have chosen to dictate that they are: same sex relationships are the most obvious one, see also premarital sex. Those prohibitions make no sense in the modern world and therefore I will ignore them.
ETA: I've always found it very telling that the first 4 of the 10 commandments are all about God saying 'me, me, me' - the stuff about treating your fellow humans decently feels like an afterthought. That isn't good enough for me.