I loved her in the role. I am a Katharine Hepburn fan saying this.

She did get an Oscar (Blanchett , I mean. Hepburn herself got 4 - more than any other actor ever).

Have any of you seen early Katherine Hepburn films, like The Philadelphia Story or Bringing Up Baby? She talks exactly as Cat B. did in The Aviator. Kate nailed the role.

Watching it now and came here to complain about this very thing. It's like a parody. Not even a parody of Hepburn but a parody of a Hepburn performance.

She was beautiful and smart.

It was slightly over-the-top, yes.
The thing is, that voice was kind of Hepburn's tradmark, but she didn't have it at this age! It came when she was older, maybe because of smoking or something, Idk. But if you see her earlier (less famous) movies, from the period she's supposed to portray here, she doesn't sound like that.
It's a disctractingly unnatural voice on a young woman.
"The best fairytale is one where you believe the people" -Irvin Kershner

Don't wanna imagine what she'd sound like in bed
Dana Carvey has a funny bit about that.

Dunno how accurate of a portrayal it was to the real Hepburn but my god her voice and inflection and mannerisms were annoying. Did men actually find that attractive back then?
Everytime she spoke I imagined as if she should be wearing a comically oversized pinstripe suit and hat with a Groucho moustache and cigar, playing a man in an old slapstick comedy and saying "YA SEE?" after everything. Don't wanna imagine what she'd sound like in bed

I found it over-the-top. It was very grating on the ears. Perhaps I need to google some Hepburn performances and listen.

I respectfully disagree. I thought she nailed the role. Maybe you just don't appreciate Katherine Hepburn. By the way, and not that it matters as you are clearly entitled to your opinion however Blanchett won the Academy Award for Best Supporting Actress for her performance. Anyway it was a brilliant film and for the record, I also enjoyed the woman who played Ava Gardner.