And micro adjusting positions isn't that hard either. If it doesn't sound right, you adjust. The hard part is figuring out whether to adjust up or down. And that's just experience. My ear still isn't good enough to know whether I'm a little sharp or a little flat. But any note I get wrong at tonight's practice will likely be a note I've hit wrong many times in previous practices.
Programming sequencers visually and with tons of help from the tooling pushes the ear sharpening later in the learning process - and I'm only now starting to realize that maybe making music is about deciding what sounds right... I suppose the trombone and violin's "sink or swim" approach ensures the early acquisition of that skill.