That’s the position of an editorialist writing in the Washington Post.  The author is a tenured professor so this is not an attack from the outside.  He argues that tenure continues to be an important safeguard of academic freedom but that

…the system has turned the academy into one of the most conservative and costly institutions in the country. Yes, conservative: Economists joke that their discipline advances one funeral at a time, but many fields must wait for wholesale generational turnover before new approaches take hold.

The system also hamstrings younger untenured professors, making them fearful of taking intellectual risks and causing them to write in jargon aimed only at those in their narrow subdiscipline: Thus in economics, people have “utility functions” instead of needs and wants.

Tenure is indeed important for academic freedom.  I have seen a few cases in which tenure insulated from public pressure academics who expressed controversial views.  However, in my opinion this is a small part of the benefit of the tenure system and in fact the editorial has it backward.

It is true that academia is conservative.  But by merely observing that

  1. We have tenure
  2. We are conservative

it does not follow that 1 implies 2.  Without tenure it would be even worse.  Basic research occurs in universities because there is a missing market:  it is too difficult to guage its benefits in the short-run.  This is often true even for insiders within the field, let alone outsiders who would make hiring, firing,  and promotion decisions based on published research.  Without a good measure of successful research, these decisions would be based on litigatable bright-line criteria which would create greater distortions in research than tenure has.  Witness that a professor of political economy would judge economists for using “utility functions.”

Indeed, the author makes exactly my point with the example of untenured professors. Only untenured professors face the prospect of having their research evaluated for promotion.  They understand very well the incentives this creates.  Unfortunately there must be one such evaluation period.  Tenure ensures that there is at most one, and that it is as short as possible.