I like reading about the development of Indo-European languages on Wikipedia and whatnot. To me, it seems that as languages go from Ancient times to the present, they lose complexity. For example, English doesn't really have a case system even though German does, Romance languages have dropped case structure despite Latin having seven, and Greek loses cases over time. Same applies to verb conjugation. English does not have genders despite coming from old German, and many Romance languages have dropped from three to two genders. Many languages used to have a 'dual' grammatical number, however this is now dropped.

Is there any reasoning or mechanism behind these trends, and does it make language more vague?