Kids do get excited when watching television, but you are right--there is a glitch in the learning process. Your daughter is laughing and cooing-- and trying to interact with something that simply cannot mirror her back or interact with her. Kids at her age learn so much from what we do, how we respond and what we do to continue that sort of fun play. We are their best, first teachers and playing with children-- or letting them entertain themselves, is one of the best gifts we can give our kids.
What I discovered in my years working with children is that TV has some serious drawbacks. If you choose to do the research, Google "young children watching tv effects". I think you will find a wealth of solid information.
We often don't watch tv at our house, simply because my son (now five) doesn't ask for it all that often. When tv is attractive, what else could we be doing instead? Right now, your daughter's task at hand is to learn about her real, immediate world. This should be her focus. Her brain needs to understand and decode what's going on in Real Life. She cannot understand the "not real" world of television and media.
Another thing to consider: is this a lifestyle/habit you want to continue throughout her life? I ask this because when we start youngsters out on tv early, they do get hooked. There is a lot of interesting chemical things that happen in the developing brain when young people watch tv. (Many detrimental effects affect the brain at all ages, incidentally.) It is worth being thoughtful about.
Lastly, Disney was successfully sued for their claims that Baby Einstein can "teach" a child. Time and again, educational tv has been debunked as being less than educational and counterproductive to actual learning. Many shows under that educational umbrella may also introduce social aggression and poor behavior that a child might not have thought up/encountered on their own. I'm not anti-tv by any means, but have come to dislike seeing children mirror many of the values that much children's media focuses on-- the most shallow parts of who we are. Children do learn quite a bit from tv, unfortunately, sometimes it is the very things we would prefer them *not* to have learned.