As @Bankai pointed out in the past, RPGs (Action or otherwise) are determined moreso by player choice (over character development and/or story), rather than the presence of dungeons, an overworld, sidequests, ect.
For example, at the end of Ocarina of Time, your Link & mine will be almost identical (with the possible exception of the of heart containers we have, and one optional sword), while in Kingdom Hearts: Dream Drop Distance, your Sora & mine are likely to very different. My deck commands may be focused on a ranged approach (Blizzaga, Fiagra, ect), while yours might be focused on up close melee combat (collision magnet, circle raid, ect), or somewhere inbetween. My Dream Eaters will be different than yours as well, which in turn determines which skills we may equip (maybe I have a fire type Dream Eater, allowing me greater fire resistance, while you might have an ice type, so on so forth).
As you can see, in Zelda, we'll both end up approaching situations & battles very similarly (due to a lack in player choice over Link's development), while in KH:DDD (an action RPG, no less), our input in Sora's/Riku's development will result in two different play styles, and we will approach the same situations in different ways.
Of course, that isn't to say Zelda is somehow less of a game (because it's not). Due to it's tighter, more "guided" structure, it allows the developers to include very complex bosses/puzzles that might be deeper than what you see in an RPG (due to having to solve the problem in a very specific manner).