I don’t know what will fix the San Francisco Giants offense*, but it won’t be the addition of two former All-Stars who have regressed to the point of being roughly average to mildly above average offensive players. That won’t fix things, but it will make things better, because even average offensive production would be a gigantic shot in the arm for the team’s lineup.
*This is a lie. I know exactly what will fix the Giants offense. A large number of good offensive baseball players will fix the Giants offense.
So don’t expect Evan Longoria and Brandon Belt to turn the Giants into the New York Yankees, but do expect them to be two additions to the lineup that at least make your heart rate drop to a normal, healthy level as you watch them take decent, reasonable at-bats.