Is there distance metric for languages that takes more than sounds into account?

I'm curious as English-speaking people often say "Chinese is the hardest language to learn", but after speaking to a few East Asian people (Thailand, Vietnam, Singapur, India, ...) , it is by far not the hardest language to learn for them.

There are languages that build their sentences completely differently (subject object verb, verb object subject, object subject verb, ...), have few sounds that overlap, express time differently or are missing some tenses altogether, change the entire meaning of the sentence by different word placement, etc.

Surely there's a metric out there that considers those things in addition to sounds and their significance in the language.