When the manner of voting for, and thus placing a Senator in office, was changed from legislative body to popular vote, the design --- the purpose of the structure --- was broken, and quite a lot of the Senate's authorization was broken with that.
For example:
The responsibilities of Senators, to their legislators back home, on matters of "advice and consent" in regard to the President, is not like their responsibilities to the popular constituency.
In the first case, the Senators are much more linked to the welfare of their home state, because they answer to the legislators whose business that is, in addition to the people of their home state.
In the second case, the Senators do not answer to the legislature, nor do they even answer to the people of their home state. Instead, the Senators answer to the polls much more on a national basis, affected strongly by the whims and wishes and directives of the national news media.
When the original intent, of the original structure, was by design, to make the Senators responsible to their home state.
Stripped of that more immediate accountability, the Senate is not performing its originally designed duties, of being a check against un-limited government and against those bent on un-limited government.
If anything, the Senate is a club bent on its being government, yet again, without personal accountability.
What the founding fathers did not want, based upon their wise failure analysis of how low the "most high" can get.
I'd amend the Constitution, but not for all the popular civil wishes and agenda that are all state matters properly within the jurisdictions of the states' common laws.
The Amendment that we need, is to return the Senators to being elected by their home state legislatures, on every other other election. That is, per Senate seat, alternate, one election by popular vote, followed by the next election by the state legislature, so forth, and so on.
It would be a compromise between the old manner of elections, originally intended, and the present manner. Yet it would give, in my humble opinion, some "term limits" control over the Senators, and over their club.
I'd recommend another "term limit" Amendment for states' Representatives, too, as follows:
Every twelve years accumulated in office by a Representative, requires that for the following two year term in that seat, the candidate is elected by the state's legislature.