The museum, which counted artists among its most active founders, has always had them on its board. In a sense their loss was as shocking as anything that came before, because it signaled in the extreme a loss of faith on the part of artists. Mr. Deitch’s tenure as director has so far been a disappointment even to the people who thought it was a feasible idea in the first place, of whom I was one.

I considered it “a brilliant stroke,” I wrote at the time, calling it an example of a museum thinking outside the box, and also an appropriately desperate measure for desperate times. The museum had come close to collapse in 2008 after drawing its endowment down to $5 million (it was once around $40 million), and there was talk of selling the collection or merging with the Los Angeles County Museum of Art. That threat was averted by the real estate developer and cultural philanthropist Eli Broad, a founding trustee of the museum, who returned to the museum’s board after a 15-year hiatus and donated a $30 million bailout, and then had a big hand in Mr. Deitch’s appointment.

I didn’t buy the idea that someone from the gallery world cannot cross over into the museum sphere or that advanced degrees in art history are essential, and I still don’t. It was certainly not beyond the realm of possibility that given Mr. Deitch’s wide art world experience he could have met the challenge of a big museum. But instead of redefining himself in a bid to do that, he seems to have redefined the job.

Rather than encourage and cultivate curators much the way an art dealer encourages and cultivates artists, he has frequently chosen to assume the role of curator himself, when he wasn’t commissioning celebrities to do it. He started with an exhibition devoted to photographs and other artworks by the actor Dennis Hopper organized by Julian Schnabel, then staged an off-site show about James Dean organized by James Franco. His 2011 “Art in the Streets” exhibition, although better received by critics and very well-attended, didn’t help establish a serious tone. And it included several artists whom Mr. Deitch had represented as an art dealer — at-best a sloppy-looking overlap between his former role as a dealer and his current one as a custodian of a public institution.