I think the distinction here is something that would enhance the game were it present, but is ultimately unexpected, often unprecedented, and superfluous and something that by its absence makes the game worse, therefore making its omission a problem.
I don't think the limited interactions is a problem, but I think Smash would overall improve with them. I don't think the lack of character DLC skins is a problem, but I think Smash would overall improve with them. I think amiibo functionality overall improves Smash, but removing it wouldn't hinder the overall quality of the game. I think the unique character entrances improves Smash, but removing them like Melee did wouldn't hinder the overall quality.
I think Cloud and Sephiroth being able to use their English VAs would improve Smash (in the west), but not having them doesn't really make things worse.
These things are supplemental to the gameplay and the core content. So having them is great, but not having them, to me, doesn't entail a glaring problem. They're like... a flourish.
I do agree this site is very inconsistent in accepting criticism, though. Many aspects of the package seem like fair game - stages, modes, ATs, items, UI, potential candidates, marketing, online especially, but then if you disparage something on the roster, yeesh, better hold on. It's a little hypocritical.