Oh look.... actors.

I know what you mean, but I think it has more to do with the fact that it's an adaptation of a stage play, which operates according to different conventions from film.

(For example: characters reveal backstory exclusively through dialog in a play rather than flashback or subtle visual "clues" common in film. This sort of expository dialog, normal in a play, feels unnatural when translated to film).

I thought both Burton and Taylor gave great performances (the younger couple is fine too), but Taylor's is the really powerful emotional center of the movie and she does a very good job. Even though I'm not sure I like the film (or the play for that matter) as a whole, Taylor embodies the lewd, slovenly, bitterly sarcastic Martha, and I was moved to tears by her description of the birth and raising of their "son" at the end.

But they were married, had a rocky relationship (they divorced and then remarried) and were both alcoholics.

Remember that this was released in 1966. Film acting back then was quite different than film acting now. It was more theatrical. A lot more stage actors were big film stars, as well, during these days. For instance, in this film, everyone but Elizabeth was a stage performer.

In my mind, Elizabeth and Richard were incredible. A bit "big" at times, yes. But, they both have plenty of wonderfully subtle moments, like George's "Bourgin" speech and Martha's description of their son, which is some of the most beautiful, moving acting I've ever seen. I can't watch it without crying.