It's far easier to change a state government than it is the federal government. The states used to be able to recall Senators if they failed to do their jobs correctly; as determined by the elected body within the state. It's simply a single level indirection of Democracy. The House of Representatives is direct. This was intentional.
What's "indefensible" about this?
And you can amend how the body is elected; hell, you can amend how the president is elected. Also Article V provides for a state "constitutional convention" as a process for initiating changes, bypassing both the Senate and the House.
For that matter, you could amend the Constitution to change the process for amending the Constitution, even to eliminate the possibility of future amendments altogether.
I was specifically referencing this clause:
no State, without its Consent, shall be deprived of its equal Suffrage in the Senate
You know, the clause that comes right after the whole "can't do anything about slavery right now" clause.
I consider this feature of the federation to be indefensible because it deprives the rights of people to equal suffrage, to the benefit of states. States should serve the rights and interests of their citizens, not the reverse.