There's a common wisdom iI learned from english.stackexchange comments that English is one of the easiest languages to learn, but one of the toughest to master. Which strikes a fair ballance. It relates for example to the relatively strict word order.
There are a number of (well sourced) posts on linguistics.stackexchange dealing with a different question, if language complexity varies, i.e. if a language could be simpler per se, which is chiefly denied. Any simplification in one part of the grammar will lead to an increase of complexity in another part.
In other words, I believe the grandparent comment cited common wisdom with a bit of folk believe. There is just no way to measure this precisely, since it is of course subjective.
There are a number of (well sourced) posts on linguistics.stackexchange dealing with a different question, if language complexity varies, i.e. if a language could be simpler per se, which is chiefly denied. Any simplification in one part of the grammar will lead to an increase of complexity in another part.
In other words, I believe the grandparent comment cited common wisdom with a bit of folk believe. There is just no way to measure this precisely, since it is of course subjective.