I think your point is that there are times when breaking the rules is a good thing. No one would argue with that. The problem is that most people have NO IDEA what the rules are for good writing. On top of that, it's easy to slip into overuse without realizing it. I'm a good writer and yet, one thing I'm terrible at is far too many adverbs. They aren't useful when overused. This app helps me see when I have relied too heavily on them.
Hemingway occasionally wrote long sentences and they proved more power because of their scarcity. The passive voice is occasionally important in good writing but bad writers use it too much. Most of the time they don't even realize it.
An app like this isn't about enforcing a standard rigidly, it's about showing an author the places in text that break general rules. It's making an author aware of the issue, not saying "Don't ever do this". In fact, the "rules" are defined as "Try to do X or fewer". The rules don't have to be followed but if you can't even recognize the rules, you have no idea when you should break them for effect.
From your example, somewhere along the way, someone taught you that long functions are GENERALLY bad (just like adverbs). That doesn't mean they are always bad (just like adverbs). This app doesn't provide an automatic condemnation of breaking the rules. It allows you to know what the rules are and how well you are following them.
Who says that the rules from the app are even right? Anybody acually eveluated them on real books by known good writers? I want statistics: how often good writers are outside promoted rules?
The rules in the app are Hemingway's rules from his book "On Writing". Lots of other authors have written similar books and generally they all agree on what works.
Henry Miller and Stephen King have both written books on the subject, and both called their books "On Writing". E.M. Forster wrote one called "Aspects of the Novel". King actually goes further, to the point of saying things like "Don't use adjectives." Extreme for most written work but if you want to get your audience to use their imagination less direction is often better.
I don't know anything about what Hemingway's rules are or what writers suggest in general. I can say, though, that during my AP English class, these are principles that we were taught in school for good writing. No doubt, you always take everything with a grain of salt so the writing doesn't have to be so rigid. But I find this app to be a great one, especially for people who want to improve and analyze their writing.
Have you ever read Tense Present by David Foster Wallace? If you haven't, find a copy online and enjoy! Based on your other comments, you'll appreciate DFW.
Short answer is that you should pardon my language, but English is fucked. So fucked that those of us native speakers should apologize for the state of our language. Not only is English constantly evolving (in different ways, in different English speaking countries), but the limited 'rules' are contradictory.
So, to answer your question about stats, we could take 10,000 English experts and lock them in a room until they write the English spec. In actual practice, they would die before they would ever agree on a set of rules. And then, even if they did come out with a spec, most famous writers would violate the spec at certain times.
I think you under-appreciate how simple English is. Sure, creating a set of rules for perfect writing is probably impossible, and in German you could probably fit them on a single page (I'm exaggerating, I don't speak German well enough to precisely judge that). But getting to a decent level of English is probably the easiest of all widely spoken natural languages. That is if we forget your atrocious non-existing spelling and pronunciation rules.
Hemingway occasionally wrote long sentences and they proved more power because of their scarcity. The passive voice is occasionally important in good writing but bad writers use it too much. Most of the time they don't even realize it.
An app like this isn't about enforcing a standard rigidly, it's about showing an author the places in text that break general rules. It's making an author aware of the issue, not saying "Don't ever do this". In fact, the "rules" are defined as "Try to do X or fewer". The rules don't have to be followed but if you can't even recognize the rules, you have no idea when you should break them for effect.
From your example, somewhere along the way, someone taught you that long functions are GENERALLY bad (just like adverbs). That doesn't mean they are always bad (just like adverbs). This app doesn't provide an automatic condemnation of breaking the rules. It allows you to know what the rules are and how well you are following them.