Does runway analysis tell me what the limiting reason is?

Yes. With each analysis, the performance limiting reason is provided along with the maximum weight. When not limited by any constraint, the aircraft’s structural weight limit becomes the limiting constraint. This is visible in the takeoff or landing view header. 

Runway Analysis supports many constraints and limiting types, including climb capability, obstacle clearance, available runway length, brake energy and tire speed limits, minimum control speed, and more. Each list of constraints possible is set by the AFM.