It works with Wine as well
A game coded in Unity has a translation layer between the Unity code and the operating system code.
Same applies with Godot, the game engine used for Angeline Era, or any other game engine.
Wine translates Windows API calls to "native Linux" calls. It turns an application using Windows API calls into a "native Linux" application.
What you're asking for is something that has the same function as Wine or Proton, but isn't Wine, and [as a result of that] is less well-tested. That testing matters. You can't just take identical code and expect it to work everywhere.
Why waste resources on creating something that's worse than a FOSS product that already exists?
That is incorrect. By definition, a native Linux game is compiled to run directly on the Linux kernel and hardware, without any translation layer.
Using Wine or Proton means you are running a Windows game; these tools are compatibility layers that translate Windows API calls to Linux ones.
This is fundamentally different from a native Linux build.
Game engines like Unity or Godot do provide an abstraction layer, but the final exported build is still a native executable (e.g., a Linux ELF binary) for the target platform. The abstraction happens at a higher level, not at the OS system call level like Wine/Proton.
I also want to add that many modern game engines do have great Linux support out-of-the-box, enabling highly-optimized Linux games with less latency and overhead and all of that with minimal development and maintenance effort.