Except, (per the VFX); the Titan's shields WERE working in the Nebula...In Ep1 Riker’s description of the ship mentions Metaphasic shields. If they can work in a star it’s likely they can work in a nebula.
Even if this wasn’t mentioned though and had background I don’t think we can count it as a goof that it was mentioned that shields don’t work in a nebula and then nearly 150 years later they do.

Technology advances in 150 years.
