Red flag laws often have some or all of these problems.

-No Due process for the accused, so guns are simply taken from innocent people and the first they know is when a cop shows up.

-No process to return taken guns or ammo after a specified period.

-Doesn't prevent acquiring new weapons.

-Little or no credibility requirements for red flags.

-These laws often don't require any sort of conviction or charge, so it's a lot like civil asset forfeiture in that it takes things from innocent people.