So you speak a V2 language like me? I'm German btw. Let me give you an outside perspective on auxiliary verbs in continental western Germanic languages:

The verb comes in second position (hence V2). Using an auxiliary verb moves the content verb to the very end of the sentence. It totally messes with the syntax.

But that's besides my point. My point wasn't that French auxiliary verbs are fancy but that fancy can me many things, in French it's the spelling and pronunciation. Cases aren't fancy, at least not the German or Latin ones. The slavic cases are a different story, in my objective opinion.