What is the importance of the 17th amendment

The Seventeenth Amendment restates the first paragraph of Article I, section 3 of the Constitution and provides for the election of senators by replacing the phrase “chosen by the Legislature thereof” with “elected by the people thereof.” In addition, it allows the governor or executive authority of each state, if authorized by that state’s legislature, to appoint a senator in the event of a vacancy, until a general election occurs.

Exact Amendment: The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years; and each Senator shall have one vote. The electors in each State shall have the qualifications requisite for electors of the most numerous branch of the State legislatures.

When vacancies happen in the representation of any State in the Senate, the executive authority of such State shall issue writs of election to fill such vacancies: Provided, That the legislature of any State may empower the executive thereof to make temporary appointments until the people fill the vacancies by election as the legislature may direct.

This amendment shall not be so construed as to affect the election or term of any Senator chosen before it becomes valid as part of the Constitution.

In the Declaration of Independence, Thomas Jefferson used his list of "facts to be submitted to a candid world" to demonstrate that the British king had been seeking to establish "an absolute Tyranny over these States" (the colonial states which were declaring their independence).  Revolution was justified if it could be shown that the British government was acting in tyrannical ways toward the colonies.

Jefferson's list included items such as:
... The king refused to assent to laws that were wholesome and necessary for the public good.
... The king had forbidden colonial governors to enact laws or implement laws without his assent (which, as the prior point noted, he was in no hurry to give).
... The king forced people to give up their rights to legislative assembly or forced legislative bodies to meet in difficult places that imposed hardships on them.
... The king dissolved legislative assemblies and then refused for a long time to have other assemblies elected.
... The king obstructed justice in the colonies and made judges dependent on his will alone for their salaries and their tenure in office.
... The king kept standing armies in place in the colonies in peacetime, without the consent of the colonial legislatures.
... The king imposed taxes without the colonists' consent.

There were more items listed by Jefferson, but you get the idea.  He was justifying revolution by proving tyranny was standard operating procedure by the British monarchy.