That's not true at all. Compared to Dutch and German for example, English contains by far the least grammatical rules.
english verb conjugation is one of the easiest of all euro languages.
when it comes to spelling english is the most difficult of all european languages.
english has been augmented by the romans with strong latin roots, viking, norman french, words from all the areas colonized by the British, and slang words from all the myriad cultures which have evolved their own specific terms. one word can have several meanings and applied in a different structure, in a sentence. the fact that english doesnt neccesarily have the most/straightforward rules can be one of the reasons its confusing/difficult to learn. i could go on, but anyway. it's not a simple language, that was my only point.