Rudy Balcers has played 143 AHL games before the age of 23 and has tallied 115 points (for reference, Drake Batherson has scored 116 points in his AHL career). So yeah, he's not Sidney Crosby, but he's also a pretty good prospect and the Sens decided they didn't need him.
There's a judgment call that has been made that they have other prospects with higher ceilings etc but that call was made without really providing Balcers true NHL minutes to determine what he was. We're going to see this more and more if they keep loading up on vets.
These decisions are going to come down to how well the Sens can internally project their own prospect careers without using NHL play as evidence and I hope for their sake they're really really good at it or else they're going to have a lot of these decisions bite them in the ass.