That Game Does Not Suit Your Play-Style
You want to roleplay a realistic character in a realistic setting. They are interested in a game with more metagame assumptions.
This is a really common situation. People enter into games expecting high drama and storytelling, and instead get a wargaming/diablo meta. Often these people do not have a gaming/crpg background, and so aren't inoculated to expect 'dungeons' and 'grinding' in their storytelling experience.
Diablo style games are much easier to run than games with realistic settings and storylines, and large amounts of the player base (especially for Dungeons and Dragons) have expectations of it to the degree that if you run a realistic campaign, they will cause problems for you, and stubbornly apply that meta regardless of attempts by the GM to get them to act more realistically (many questions on this site from GMs trying to address this).
My Advice
Don't expect a high level of realism or storytelling from this group. They are going to want to 'kill the monsters' and 'collect the loot'. There will be a story, but it will largely be the purview of the GM and not the players - choices are unlikely to be meaningful, and from the player reaction to your injection of realism, that's the way they want it.
What You See Is What You're Gonna Get, basically.
If you want to find another game group more interested in realism, i'd start by looking for people (ask at your local game store, look for groups of gamers that meet up, check out a convention) playing a game other than Dungeons and Dragons. Although I personally love combining the associated-rules-heavy nature of DnD 3.5e and Pathfinder with realistic character portrayal and choices to create gritty 'The World Is Dark And Scary, But You're Badass' games, the vast majority of players and GMs are playing Diablo games and only want to play Diablo games. Finding DnD players who like gritty realistic games is quite hard. Generally they will accrete into a group, but finding that group in the noise is very hard.
People playing FATE, Dogs in the Vineyard, Deniable, Rapture, Unisystem, Paranoia, Truth and Justice, Rogue Trader, Shadowrun, so forth, will be more likely to have a more realistic storytelling style that you will prefer. They will at least know people who play in that style, and you'll likely be able to find a DnD group that uses that style through them.
People Saying You Are Wrong And Bad
Many people are very defensive about playing Diablo style games and insist they aren't while still doing it. This is due to a lot of factors. Be aware they will do this, try to avoid getting involved in any debates on the subject. It is not an argument you can win, much like those involving religion, or politics.
'The OP might be wrong about the group' 'The OP shouldn't write off the group'
No. There are lots of groups like this in the roleplaying community. There are more of them than there are any other kind. It is unlikely that he is wrong after observing them and given the % of groups like this.
There is a large feeling in the roleplaying community that you should 'do what the group wants' and 'stick with the group' growing partially out of how hard it is to find a roleplaying group, and partially because people assume anyone with a different expectation or style is 'That Guy'. The OP is clearly not 'That Guy', and we know nothing about his whereabouts or ability to find other groups.
Clearly, if this is the only group for hundreds of miles and he cannot ever have another group, he will simply have to decide if he's still enjoying it enough to stick around.
But in my experience, most gamers who ever get a group tend to live in metropolitan areas with more than one gaming group available. Also, they tend to stay with the same group due to uncertainty and the aforementioned community attitudes, and therefore miss out on their preferred playstyle.
I have found, by talking to people who I introduced to roleplaying who later stopped doing it, that by far the largest cause of them leaving the hobby was the group/a group that played a different style than they did, and a lack of confidence in looking for another group with the same play style as them.
Play style, the style of the game, is incredibly important. If people are not on the same page as you, you will not have as much fun.
Having the confidence to go out and find a group of people you will have fun with is paramount, and advice to 'stick with it', while sounding very upright and community-minded, is about the worst thing you can ever do in terms of the individual getting enough out of it to justify pigeonholing a weekly time for the game.
Sources: Playing a variety of game systems with literally hundreds of different people, in a variety of styles (including diablo-style hack'n'slash, which I quite enjoy), witnessing this specific phenomenon, working with others to create style preferences and guide people to groups that support their gaming style.
