I've mostly seen the term in regards to game design i.e. a game having a steep learning curve means that it's hard to get into because it requires the player to have a lot of understanding about the game's mechanics before the player is able to realize his/her intentions inside the game with predictable outcomes.

In that context having a "not so steep" learning curve can help players ease into a vast, previously unknown, ruleset much easier by introducing it piece by piece, instead of literally overwhelming the player by throwing all of it at him/her at once.