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

I'll name two things: 1) Government pay 2) Government shutdowns

But regardless, this was a Boeing spacecraft; it wasn't built by NASA (NASA generally does systems engineering; contractors build things like this).

A government shutdown is a basically surprise paid vacation, as long as you have enough cash to skip a couple paychecks.