So out of simple self interest it behooves us not to just say "the status quo should be hard to change". When we see an injustice, we should fight to change it, even when it's not to our own immediate advantage.
It is an amazing read, but the things that stand out to me are these.
1. Have diffuse/decentralized power centers to make it harder for special interest groups to gain power and control things. The last two centuries have had a tendency to move power from states to federal government; and from Congress to the President. So the balance of power has centralized.
2. Avoid a direct democracy because they tend to get subjected to demagogues. The direct election of senators was a major turning point in helping centralize power; since states became more and more irrelevant.
I am always impressed by how much Madison understood the nuances of political power and tyranny.
[1] https://billofrightsinstitute.org/founding-documents/primary...
This is the overall design.