[thaumasiotes]

> The printing press froze the written German language before natural language evolution had a chance to simplify the declensional system.

If natural language evolution had any tendency to simplify the declensional system, German would have been born with no declensional system. There was plenty of time. That just isn't how language change works.

[euroderf]

Data point: Icelandic and Lithuanian are very conservative Indo-European languages; Icelandic and Lithuanian are grammatical nightmares.