I'm sure it would be very frustrating and disheartening to perceive that DMs and game designers are actively punishing players by restricting fighters from hill cutting and chasm leaping.
The way I see it is that verisimilitude (not realism per se) already has a baseline or reference point -- real life and/or action movies. Magic has no consistent reference point, so it's not the same uphill battle. For superhuman abilities, I then have to be sold (either through sheer ignorance or suspension of disbelief) on raising to bar for what I want to have as superhuman-possible in an RPG.
Real life and action movies are your baselines? You need to broaden your horizons a little. I draw my inspiration and expectations from history, mythology, classical literature, movies, anime, videogames, and novels of all sorts.
Sheer ignorance: in action movies, people fly through windows all the time and get back up. Realistically, hitting and shattering glass can actually be quite crippling. Who knew? But it never bothered me because I've accepted the trope already and was ignorant of the realism and, well, it's not really a big deal. (I have to smile when people write that PCs aren't superhuman until 5th level or so... I think they're already superhuman at 1st level).
I am pretty sure that everyone knows that broken glass can cut people up badly. I think the "ignorance" argument you are making here sounds like you are looking down on other people, here... I hope that isn't what you are getting at...
Suspension of disbelief: If someone said "it's not fair", well, that may be true mechanically, but it would never change my mind about what I ideally want for fluff. Sell me on the fluff fairly and I'll buy into it. Guy Gavriel Kay, for example, in the Fionavar Tapestry does a tremendous job on selling me a vision of ultra-skilled warriors that I bought into it hook, line and sinker.
Read some actual mythology and classic literature then. When I mentioned the whole "slicing a hill in half", I was actually making a specific reference to the Táin Bó Cúailnge, the Irish epic that chronicles the story of Cú Chulainn and other heroes. Half of the Táin consists of fights between various Irish warriors that are used to explain various distinct landmarks in Ireland. Why does a certain hill have a flat top? Because an Irish hero hewed the top of it off with a spear.
If you were to read the Iliad, the Odyssey, the Arabian Nights, various significant Chinese novels, mythology of all sorts, and so on, you would be exposed to all sorts of amazing feats such as these.
For example, the great Chinese Novel known in English as
Water Margin or
The Bandits of the March, has various sorcerers, Buddhist priests, and Daoists in it who can transform things, create illusions, and run like the wind. It also has heroes who can lift boulders the size of houses over their heads or defeat an entire army by throwing stones.
One of my favorite examples comes from the Hindu epic: the Ramayana. At one point in the story, the monkey Hamuman literally tears a mountain off of its foundation, and jumps with it on his back a few hundred miles.
These kinds of stories, the sort of stories that D&D draws a huge amount of material from, make me okay with fighters who can do cool things.
I don't think that the craving for verisimilitude is unreasonable, especially the idea of fighters slicing hills in half. Sell me on it. Hit the fighter with gamma radiation and turn him into a hulking green-skinned brute or something other than "it's not balanced / it's not fair" (I'm not quoting you, I'm just paraphrasing the general argument I think I'm hearing).
Game balance is a much more important concern than verisimilitude. Unlike verisimilitude, which is a strange, hard to pin down thing with an iffy impact on playing D&D, game balance is something that is critically important to game play. A lack of balance can directly lead to problems at the table. You cannot use verisimilitude as an excuse for horrid game balance.
Anyways, if you think that comic book science is necessary to justify fighters doing cool stuff, you really need to read more classical stuff. I strongly suggest you read some of the things I suggested above. If you want to start at the deep end, read the Ramayana. If you want to start with something more familiar, read the Táin or Beowulf.