Is there any software that does take toolpaths into account?
Not as far as I know. The next best option is to define anisotropic properties in the z-direction but this doesn’t close the gap between simulation and slicer output.
How good is it? Good enough. Work with safety margins and temper the print if it is close. An important aspect to make Ansys, Nastram, … work with FDM is experience/rule of thumb. Knowing how to read the result and how to set up a simulation/model to get close enough results.
Most valuable is where and how it will fail as this is pretty accurate. For the exact load capacity it is the simulation result decreased by some rule of thumb based on experience.