The article explains it fairly well. The SLS organization is a disaster. Not that this is unexpected.
NASA’s Office of Inspector General warned that Ground Systems Development and Operations, or GSDO, may be hard-pressed to have Kennedy Space Center's launch facilities ready on time. ...
"GSDO cannot finalize and complete its requirements without substantial input for the other two programs," said Jim Morrison, the assistant inspector general for audits. "And NASA is still finalizing the requirements for those programs."
In other words the pad work is delayed because they haven't finished the rocket design yet. And this is like 3 years before the launch.
Historically, said the OIG, NASA has taken a more centralized approach to the management of its in-house launch programs, synchronizing development activities through a single contractor. This is not the case for SLS, Orion and GSDO—each program is managed independently, with an emphasis placed on cross-program coordination. The OIG believes this approach is inefficient and could lead to scheduling delays.
I suggest NASA reads this paper:
Bayer, Martin. "Hermes- Lessons learnt." IAF, International Astronautical Congress, 45 th, Jerusalem, Israel. 1994.