You're right, and this is something we've discussed a bunch. Our current view is that:
1. Allowing teams to standarise on an _approach_ and a library in the first place is a huge step up from individual ad hoc implementations.
2. If you have shared logic between applications, you can still write language-agnostic policies and share those between them. If there are parts that are specific to an application/language, its easy enough to pull these into separate rules and add shims.
3. We intentionally wanted to keep the language lean to lower the learning curve. But we're considering adding a standard library in the future, powered by the Rust core, to provide common functionality. The nice thing is that you're not limited by how fast we add those.
We're interested in hearing from folks who are working in those environments to hear what would make the most sense for them.