Most pragmatic stage bans/counterpicks boil down to how maneuverable you are vs how maneuverable your opponent is.
Fox, for example, is arguably at his best when he has a lot of room to run around and/or a lot of terrain to hide behind/on. Stages like Pokemon Stadium, and FD are preferred by many fox mains because they can always run away from their opponent and force them to approach using lasers.
Smaller stages tend to favor slower characters slightly more, as their hitboxes comprise a larger part of the stage, leveling the playing field somewhat against more maneuverable opponents. If you were marth, picking Yoshi's story against a campy fox could be considered a strong offensive counterpick (your hitboxes are huge on that stage, you can platform kill off of tech, low % KOs on any char). Conversely characters like jigglypuff or peach (and fox, if you like to be a campy *******) can pick large stages like dreamland or kongo jungle (if legal) and live to very high % without damaging their KO potential substantially, this would be considered a good defensive counterpick.
But like people have said already, you should play on whatever stage you're comfortable with. But keep in mind character factors and try to practice most on stages you're weakest at, you WILL get counterpicked there eventually.