Assassination Rogue is recommending item level gear a few hundred ilvl below the maximum for Dragonflight (ex: Shadowlands legendaries and Legion Artifact Weapons or Trinkets). In todays sim, the website completely broke and I was prompted to make a forum post with the snapshot ID.
We will be doing an update later today before the servers come back up. If you are still having this problem after the update, please let us know and post a snapshot. I can’t load this snapshot anymore on my development version because we have switched over to the 10.1 talent trees.