The optics of them doing something for the “good of society.” We all know that the only people affected by things like this are law-abiding gun owners and sportsmen and women.
From the OP's linked article, a few choice quotes:
Assault weapons ban: The AG’s office states that assault weapons are semi-automatic rifles with at least one military-style feature that make the firearm shoot more accurately and rapidly. Noting that less than 2 percent of Americans own such guns, the AG’s office will recommend a ban of assault rifles in Washington in 2019.
Ghost guns: “Ghost guns” are essentially untraceable firearms that are ordered through the mail, and often made with plastic using a 3D printer. The issue surrounding ghost guns arose in 2018, and prompted legal action. The AG’s office will recommend a ghost gun ban in 2019, prohibiting the ownership or transfer of any firearm that cannot be detected by a metal detector, and increases the criminal penalty for using an undetectable gun in a felony crime.