He's absolutely soft, anyone debating that is living in fantasyland. But soft players succeed in the NHL all the time, it's not a trait that disqualifies you from being a successful player.
@OgeeOgelthorpe is right, the thing that is currently disqualifying him from a real NHL role is his embarrassing lack of compete. He's a giveaway machine without even touching the puck because he gives up on battles that he should otherwise have
at least a 50/50 chance of winning due to his speed. He tilts the ice in the wrong direction this season.
He's been compared to Nyquist a lot on this forum in the past, but Nyquist, who's also a soft player,
had very good compete (same with Tatar). And that's basically a requirement when you're smaller and softer than average. If Berggren can't up that part of his game, he's useless to Detroit and they should absolutely package him up for an upgrade somewhere else on the roster while he still has perceived value.