Not so, dear sir!
English does have plenty of rules. The problem is that you need to know the etymology of the words you’re using to work out which rule(s) apply.
English is a whore: it’s never met another language it didn’t like. It is an amalgam of Old French, Frisian (from Germany’s north-western coast), and a bunch of loan words from a myriad other languages and cultures. Note that the Romans had very little influence on English: Latin was the language of the learned religious clergy, not the unwashed masses.
The Victorians had a couple of fads revolving around Latin. Until that point, the English used “fall” to represent the season before winter, just like their American cousins. Afterwards, “autumn” became the accepted term.
In addition, many scientists during the Renaissance era had a classical education, which resulted in many fields of science using old Greek and Latin words and stems in their jargon.
Loan words often cause the most confusion. In general, a loan word may be:
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Not yet “naturalised”, and thus its own language’s rules for plurals, etc. apply. (This is mostly seen in technical jargon, such as “flora” and “fauna”, both from Latin.)
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“Fully naturalised”, which means English rules do apply. (E.g. the plural of “forum” is “forums”, not “fora”, because “forum” is a naturalised word imported from French.)
(The above also applies to other languages: “Cliccare il mouse”—the Italian for “click the mouse [button]”—shows a naturalised loan word, ‘Cliccare’, which uses Italian phonetic rules, and the unnaturalised “mouse”, which has retained its English pronunciation.)
In general, the word’s origin and state of naturalisation will define which rules apply to it. The problem is that the etymologies can be very complex, with some words having multiple threads of history for each of their senses. (‘Chair’ is a good example. The furniture is from Old French, while the sense of a ‘seat’ as in ‘seat of authority’ comes via the Latin ‘cathedra’—from which we get ‘cathedral’.)
English spelling is worse. It was fixed quite late in life—the Italian of Chaucer’s time is perfectly readable today, yet Chaucer’s English is like a foreign language to most readers now—and was undergoing some changes when the first attempts to lock it down were made. Hence the fact that “ghoti” could be justifiably pronounced “fish”. (As in “cough” + “women” + “attention”.)
The problem is therefore not that English has no rules, or even very few rules. The problem is that the full set of rules is so complex and difficult, that even experts find it extremely difficult to master them all. The user interface has become very complex.
“Legalese”, on the other hand, is an attempt to create an unambiguous programming language for humans out of English—arguably the most ambiguous natural language known to humanity.