"It is what it is" is not about accepting the reality that you've been given.
It's a litany against perfectionism. It's, "I have done all that I can do toward (project/topic) and worrying about it further won't help me."
It hit the zeitgeist in 2006 when contestant Dave Martin said it on season one of Top Chef, regarding a challenge that he realized he was needlessly stressing himself out over.
If there is something more than you can reasonably do, then "it is what it is" does not apply.
Yes, this is still about Dimension 20.
Sofie is right. While it is a powerful litany against perfectionism, it's a stupid mantra for any organization with an ongoing mission.