WordPress itself can handle lots of traffic if scaled correctly. However, if you're looking to do lots of custom features that don't have WordPress plugins for and require custom work, then you're probably better off with a custom product.
There’s a caveat that you have to start on an older version of Nodebb, but:
Import your forum data to nodebb
A xenforo to NodeBB data exporter
Edit: looks like it was updated to support a more recent version of NBB