My 2 cents...
The Preamble of the Bill of Rights was important, especially at the time the Bill of Rights was passed. Actually it was a "big ****ing deal" because adding the Bill of Rights barely passed by only a handful of votes, according to the history books. Madison is basically given credit for it passing. Not because of any of the content that he contributed to the creation of the Bill of Rights, but because of his negotiation skills and his calm demeanor that acted as sort of a firewall between opposing parties during debates.
A lot of people of the time didn't want to wind up with a Constitution that only outlined the role of government. Despite that, there were a fair number of the Framers who were against passing it.
What makes the Preamble of the Bill of Rights important today, as in past times, is that it serves as sort of mission, core values, and vision statement all rolled up into the first paragraph in the Preamble. It reminds us of its intent by the Framers who supported adding it to the Constitution:
"THE Conventions of a number of the States, having at the time of their adopting the Constitution, expressed a desire, in order to prevent misconstruction or abuse of its powers, that further declaratory and restrictive clauses should be added: And as extending the ground of public confidence in the Government, will best ensure the beneficent ends of its institution."
Thanks.