That's the fundamental equation, and it generally assumes a vegan diet as well. Nobody has ever been able to reduce this value, it's related to the solar input and the ability of plants to capture carbon into a human-digestible energy source.
It'll be worse on Mars, of course, due to the reduced intensity of sunlight.
In any event, 17 acres could theoretically supply food for an enormous range from 15 to 170 people, depending on how intensively it's farmed.
[1] 4000 sq ft bio-intensive farming (http://www.growbiointensive.org/) [2] 0.44 acres permaculturism (https://permaculturism.com/how-much-land-does-it-take-to-fee...) [3] 1.2 from a 1994 study (and further discussion in this reddit thread: https://www.reddit.com/r/askscience/comments/1aozn1/how_much...)
And meat also provides an excellent nutrient:calorie ratio with extremely low upkeep. You can sustain around 50 free range chickens per acre, and they're ready for harvest in 6 weeks. That's more than a whole chicken per day, on a single acre. If you want to get real crazy you can also get into things like vertical farming/aquaponics [2] and more, where the densities are limited really only by cost. Though on the still very reasonable end, you can do things like potato boxes where you can get hundreds of pounds of potatoes in tens of square feet.
https://www.rga.org.au/Public/Public/Content/The_Rice_Indust...
I'm not sure where you get your odd notions from.
Of course you can also plant rice on flat fields (and China does as well), but this does skew the comparative ratios of acres of land use : people fed.
Maybe you're thinking of some specific subset of urban western non agricultural people.
Of course in western culture the "typical" westerner lives in an urban environment so perhaps that explains the disconnect.
Do better.
Everybody I've met in 60+ years considers the land that rice farmers farm rice on to be farmland.
Perhaps you might do better policing others less and working more on making a point.