With that being said, Gostisbehere is not proving the Flyers wrong, but every team in this league also. The defenseman has 40 points in 63 games this season.
That's more than every defenseman that the Flyers brought to the team this summer. His underlying stats are also better than all of them. In the goals against category, only Ellis has better numbers, but he has played a lot less games than Gostisbehere.
The presence of Gostisbehere at the Flyers' blue line wouldn't have changed a lot of things this year, but you can argue that he would've helped in a lot of ways, especially on the Power Play.