Our system as it was created is perfectly fine and scalable, with maybe a few changes. The problem is that system has been altered in so many different ways now that it isn't what people think it is.

Just for example: senators used to be chosen by state legislature. That kept them more accountable and kept their terms short. It meant they were harder to buy off by big corporations because they were just going to be gone soon anyway (a lot of times in less than there full term). After that was changed, via constitutional amendment, was when we started seeing senators staying in for 20+ years. They never have to see the people who voted for them, and they aren't accountable to their states ruling body. Graham or McConnell couldn't exist in the old system.