Yes, it has been a while since it was successfully amended: the last amendment passed in 1992, but even that one had been hanging around since 1791. The last new amendment to pass became law in 1971.
The delay is not just because politics has become more of a zero-sum game. We have gone through plenty of such phases in our history. The problem is more that the amendments proposed have not attracted the super-majority of support necessary, usually because they are proposed by one party to benefit primarily that party’s supporters.
This amendment is different. Broadly worded as it is, it still addresses a rare problem. The last presidential family member pardoned was Roger Clinton in 2000. The last president to pardon a member of his administration was also Clinton, in his pardon of Housing and Urban Development Secretary Henry Cisneros in 2001. (George W. Bush commuted the sentence of Scooter Libby in 2007, but did not pardon him. Trump granted Libby a full pardon in 2018.) The Cohen amendment was written as an attack on Trump, but all it is really is a sensible narrowing of the president’s power, something Republicans would typically support.