The usual reason for the issue you’re reporting is not your legendary gems or the base CR of your items. Instead it’s…
Rank of Set Items
Rank of Legendary Items
Warband Tableau level
Helliquary level
As you’re finding out, catching up on these is hard time-gated and there are no catch-up mechanics for some of these, meaning you’re essentially many months behind no matter how much time / effort you put in.