I know this isn't what you want to hear, but they are basically saying that you wouldn't be a good fit with the team.
Now as for the exact reasoning they will probably not tell you, as ambiguous rejections are easier to manage. But to me that sounds like they think you need guidance / support that they cannot offer (read: don't have the budget for).
Not saying I agree with any of it, mind you. Just giving my interpretation
If done well it's called constructive feedback, not bad communication.
The problem is that many folks feel like it's the only feedback tool in the toolbox, and the praises can seem less sincere over time, as some managers think they need to find something positive every single time. This can make it less efficient or sincere, so it's good to have some variety.