Yeah, it seems harsh, especially after-the-fact. Many other examples when fans are guilty of overkill long after the horse has left the barn. (And I've done it, too).
My assumption is most fans who bring up players like Holden are second-guessing a coaching staff's decision to sign someone or criticizing how a player was incorporated into a game plan or rotation — not a knock on the player himself. But it doesn't usually translate that way, it tends to feel like a personal attack on the athlete.
I don't really think it's as much about Holden as it is commentary on the ability on guys on that level moving to B12 play. Holden isn't a scapegoat, he's a cautionary tale.