If it makes anyone feel better, in Belt's monstrous 2021 year he still started off very poorly.
2021: 11 games, 25 plate appearances, 2 singles, 1 homer, 4 walks, 10 strikeouts
2023: 6 games, 25 plate appearances, 1 double, 2 walks, 15 strikeouts
Seeing some SF fans on reddit say he seems to always start off very cold. He's not a lost cause yet... give him at least a few weeks