(side note: To reply to all the folks who like term limits, I ask again, has term limits helped the government of California?)
To reply to the OP, the two biggest differences I see between 1776 and now are population and transportation/communication technology.
Which gives rise to the following proposal: eliminate the geographic aspect of representation. At least for the House.
331,000,000 people in the US, 435 representatives = 1 rep for every 750,000 people (rounding freely)
How about a system where each member of the House represents people directly rather than representing a district.
Every person who can present a petition with the signatures of 500,000 citizens is a member of the House.
Every citizen gets one signature.
Citizens “sign a petition” only once every two years.
That congress critter represents those 500K people directly,
That gives me the choice to find the politician who represents my views on foreign policy, the military, immigration, vegetarianism and what ever else I find important.
And my views aren’t diluted or deflected by my neighbors.
If Jane Politician finds 500,000 people who thinks she should be in Congress, then she goes to DC.
I am directly represented, not based on my zip code, but based on my opinions.
If Jane Politician has 1 million folks who agree with her… either we (her supporters) hunt up Jack who agrees with us and half of us sign his petition or perhaps Jane holds two seats.
The ongoing mechanics of keeping the House membership small enough to work (i.e. adjusting the 500,000 to increasing population) and such is not the core of what I’m suggesting.
The world of 2020 is so different from the world of 1776, that a contemporary expression of the values of the Founders can’t be achieved by tweaking the procedures of 1776. The change in procedure has to be as radical as the change in technology and population has been.
Direct representation of groups of individuals should replace representation of geographic sub divisions.