Bills have a lot of complexity that make them difficult to pass, separate from simply agreeing on the foundational policy ideals that the bills mean to support. There are many steps in the process whereby congressional representatives can put stop gaps in on certain bills, and also where people can give public comments or testimony. When a bill fails, I don鈥檛 always believe that it is about a disagreement about the big picture ideology, but it is rather about the law within the bill or whether various parts of the bill support all policies.
When I worked for the Kansas Legislature, I sat in on the House Judiciary Committee, which gave me an appreciation for just how intricate law is. Once, the committee passed a bill and then had to backtrack because they realized that they had accidentally made something legal that they really didn鈥檛 want made legal. The law has a lot of loopholes and it takes a well-informed mind to understand all of a bill鈥檚 parts. If there is a loophole or error in a bill, that is a chink in the legal armor, so to speak, that I would hope our representatives are working to fix.
There is a great YouTube channel called Crash Course that provides educational videos about various topics. I really recommend How a Bill Becomes a Law and Congressional Committees, if you want to delve deeper!