When you sign #6 Ds who can't move the puck up ice, it is hard to score because you are defending a lot.
Also, the only players scoring are the star players, what we spend on depth scoring is not that bad, our goalies are very cheap, for reference, Florida spent $9 million more on goaltending last year, which basically voids Marner's contract and we still can't find depth.
Treliving spent over $50 million, he had a chance to change things, but he chose not to.
We've had this issue for multiple GMs, this isn't specifically Treliving, but depth scoring is always bad and every year we focus on D.