“White is not supposed to be better than black at creature destruction,” Says who? Swords to Plowshares was an Uncommon in Limited Edition and Ice Age while Terror was downgraded to Dark Banishing at the same time. It seems like White should have equal or better removal than Black, and the color pie doesn’t fall apart if that’s true.

Swords to Plowshares is considered to be a huge mistake because white eclipsed black as the creature killing color and that wasn’t the intent.

Does the removal of regeneration as a modern mechanic mean we won't see reprints of Terror/Dark Banishing again?

Not in Standard legal sets.

As a kid I loved the watercolor art by Drew Tucker on lots of old cards like Dark Banishing, Necrite, Leshrac's Sigil, etc. Over time, Magic's art has grown a lot more heavily curated and we don't get the cool outside-the-box stuff like this as much. What are the chances we ever get some of that back?

Magic has chosen to take a path where the art has a more overall cohesive feel. This helps us create sets and blocks that have a stronger visceral feel and give the sense that they all are happening in a unified world. I too loved Drew Tucker but I think this sacrifice is for the overall greater good of the artistic quality of Magic.

You say you wouldn't have named a creature that unsummons other creatures "Banisher." I think you forget that, since Dark Banishing back in Ice Age, a host of cards have used "banish" with the flavor of either bouncing or putting the creature back into the library. Examples of bouncing include Banishing Knack and Surrakar Banisher.

Three wrongs don’t make a right.