The problem with the Belt signing is that he doesn't provide any value to the team outside of his bat. If someone like Gallo or Bellinger or forgets how to hit, you can still stash them on the roster as a defensive replacement/pinch runner and hope they figure it out.
If this is a timing/injury recovery thing, Belt needs to face live pitching to get out of it. But I don't think we can give him too many more major league PAs to figure it out. These are the kinds of decisions that can cost you a pennant at the end of the year.