Republican presidents are at fault too. Many times they nominated bad candidates. President Reagan nominated Sandra Day OConnor when he had a Republican majority in the Senate. President George H. W. Bush nominated David Souter instead of Edith Jones, who is a rock-ribbed conservative and who is said to be a runner-up for that vacancy. President George W. Bush nominated John Roberts instead of Michael Luttig, who would be much better.
Was Brett Kavanaugh the best candidate for Anthony Kennedys seat? Personally, I would have chosen David Stras, who was Clarence Thomas clerk, but seems to be well-liked and uncontroversial, instead of Brett Kavanaugh.
If you listen to Mark Levin, who vetted Souter for Bush, you will see that Souter lied completely and totally deceived the conservative team created to ensure we get a constitutional originalist.