English is one of the most difficult languages to learn, because there's so many irregular sentence/word constructions + irregular pronunciations due to vowel shift + foreign loan words like French/Latin that must be pronounced differently.
Mandarin eliminates all of these problems. The tones and characters are difficult, sure, but questions and answers being grammatically identical along with consistent pinyin is a lifesaver.
English is the best language for this because it easily incorporates quirks/foreign loan words. It will always win over more perfect languages because it just absorbs new concepts. It's purpose/existence from the start was to absorb cultures/concepts. It IS the embodiment of joining cultures + move fast/break things over entrenching/codifying.
Most of that is due to weird spelling, not inherent to the spoken language.