There is descriptive linguistics and prescriptive linguistics (and that applies, in particular, to lexicography); but to make sense, to create rules people will not immediately and fully ignore (merely somewhat in some relatively rare cases as the language changes), prescriptive linguistics feeds on descriptive linguistics to prescribe something not too different (which does not say “the same”). Thus to create a dictionary which will unify common usage you need to describe common usage first—not to be too astray.
Unfortunately, in English tradition this is also blurred by having no usual distinction between prescriptive grammars (and lexicons) and style guides.
There is descriptive linguistics and prescriptive linguistics (and that applies, in particular, to lexicography); but to make sense, to create rules people will not immediately and fully ignore (merely somewhat in some relatively rare cases as the language changes), prescriptive linguistics feeds on descriptive linguistics to prescribe something not too different (which does not say “the same”). Thus to create a dictionary which will unify common usage you need to describe common usage first—not to be too astray.
Unfortunately, in English tradition this is also blurred by having no usual distinction between prescriptive grammars (and lexicons) and style guides.