> Reputation for overcomplexity, loss of users. Becoming the next C++ or Haskell.
I think Rust is already there. It's a concern, but I'm not sure you can or should try too hard to avoid this.
What you can do is look to make simplifications as you add complexity.
And sometimes innovations can have simplifying effects. For example, the various "effects" libraries for Haskell simplify I/O code compared to not having them.