The English language has no "rules" like you describe. That's called prescriptivism, when individuals make up "rules" to tell people how to speak or write. There ARE some uses for that, such as standardization and formal writing. But creativity is at least as strong a force in all language use, and as you point out, the rules aren't very consistent, and that's simply because they don't really exist. They're opinions, very often based on weird ideas (like thinking that English should resemble Latin for some reason), and they're so poorly founded that even those in general agreement about making these "rules" don't know which ones are "important". Others have just caught on for not particular reason (because they've been said enough) and are entirely irrelevant, like not splitting an infinitive and not ending a sentence with a preposition.
If you want a linguistic perspective on prescriptivism, you might really enjoy a good book about the subject:
Anne Curzan (2014). Fixing English: Prescritivism and Language History.
What's especially interesting about this book is that it doesn't just attack prescriptivism but talks about some of the good uses and effects of it as well.
There are plenty of other things you can read about prescritivism vs. descriptivism (descriptive linguistics, the overall focus of this forum).
