The problem with the Senate is the 17th. The Senate's job in our republic is to represent the interests of the states. When state legislatures decide, they put the old ones to pasture, even if only to further the careers of themselves.
Another way they could improve would be to have committee assignments and leadership based on rotations derived from the district being represented. In other words, hypothetically, the representative from the 33rd district of California will serve as the vice-chair of the Rules Committee in 2025, regardless of who wins the next election. Less incentive to keep returning experience. Also need to completely get rid of pensions for public service. If SocSec and 401K are good enough for most of us, they are good enough for them.