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> Since the orbital dynamics are very well understood and there really isn't anything that can affect the motion of the spacecraft other than engine burns

This is wrong.

1) Atmospheric drag (unless you're in really high orbits)

2) Wind

3) Uneven gravitational field. Our planet is not a perfect sphere. The moon is even less so.

4) Solar pressure (though very minor and kinda evens out in orbit).

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The unevenness of the gravitational field on Earth is for the most part ignorable. It isn't like maneuvers are precise enough that one could account for it in the calculations anyway.

Space is empty enough and engines imprecise enough that for orbital stuff you have enough margins to correctly predict and plan a trajectory ahead of time, and just do correction burns later if necessary.

On the Moon the gravitational field is indeed uneven enough to matter, but exactly one orbiter really cares about it (LRO iirc has a specific orbit where the unevenness mostly cancels out), most simply rely on occasional station keeping burns.

Which of these can't you calculate ahead of the launch? Numbers 1, 3, and 4 seem like you could calculate it ahead of time. And maybe number 2 as well, if you do it relatively close to launch time.

They use models. No model is perfect, they all have uncertainties.

Which is why they use pilots too

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