Flight Simulator 2024’s Career Mode should’ve been an add-on

It’s a bit more complicated than that.

https://www.x-plane.com/pro/

It enables a couple of features:

  1. It provides hardware and frame-rate checks required for FAA certification of the simulator.
  2. It unlocks features of the simulator not available in X-Plane 12 Global. Specifically – the ability to use cylindrical and spherical projection (as found in large simulators).

You then need to spend a small fortune on approved hardware, then get it vetted on top of that.