The Longest Year in Human History (46 B.C.E.) - https://youtu.be/fD-R35DSSZY gets into the "why the year we have is designed the way it is" ... though it takes 22 minutes to get to that part.

It wasn't really better as the 30 * 12 + 5 approach needed manual application of the + 5... which is what the new calendar was trying to avoid.