'Select attack....wait....get attacked....repeat' *yawn*
Not all RPGs are like that, you know. Many can be just as action packed as other games of different genres, especially action RPGs like Secret of Mana, Diablo, Mass Effect, possibly Crisis Core (I heard it's got action packed gameplay) and Super Paper Mario. I think you're generalizing too much. It's like if I made a thread saying all Strategy games suck because they're "too slow," when, in fact, there are plenty that are fast paced, I just didn't bother to look outside of Civilization and other turn based strategy games.
well in zelda the emphasis is not on story but gameplay, immersion into the game of THAT world is all about the great sense of adventure you get in controlling link and having the freedom to explore a world through him.
immersion into an rpg though is as you said...totally related to the story line of the game, story taking the place of gameplay is a concern I have in all games...even mario sunshine made me watch some really boring opening cut scene when all I wanted to do was get started with the game, and this problem is seen on a much more extreme level on metal gear solid 4 where it seems people will be subjected to 90 minute cut scenes....but at least those games have interesting and fun gameplay mechanics in between time...RPGs are just repetitive, slow, boring, and tedious.
People love a reason to play, to keep going. Stories are one of the main driving factor for this. You want to see what your character is like, how s/he is dealing with soandso or suchandsuch, and, more importantly, you want see what happens to her/him as you progress through the game. What changes, what doesn't, how s/he interacts with others, etc. You get immersed into the game more because of the story in RPGs then of the gameplay because many RPGs have characters or even plot that you care about. When s/he levels up, you feel proud of yourself. When s/he overcomes a big bad boss, you feel glad that you were able to bring her/him the whole way there and help accomplish personal goals you've made with the character. It's like D&D, which is the granddaddy of RPGs (I think?); you don't focus as much on rolling the dice as you are on roleplaying your character. If your character is a sneaky, backstabbing, lawful evil kind of character, you're going to have fonder memories of when you lead your party into a trap then, say, rolling criticals on a high level creature you were fighting. If your character is a mage, you're going to be more excited when you find a great spell book then when you rolled a 20 on climbing a building. So on and so forth.
Point is, RPGs are suppose to get you immersed into the story so much that you'll forgive them for their faults and don't mind grinding for 10 minutes or so to get to the next level. Or, well, most of them, anyways. The good ones find at least the perfect balance. Either their story is good enough that you don't mind the lackluster gameplay, or the gameplay is alright, and so is the story. The great ones, however, excel in both.
I hope that made sense for you.