There are some not so good TAs and some that are great. It sounds like the PP's friend didn't get a good one. That is sad and makes it harder on the ones that are great at what they do.
What should happen when you use a good TA is that you should never pay more with them but you could pay less. They do as much or as little as you want them to do. If you like making your Fast Passes or your dining reservations, that's not a problem. If you don't want to do that yourself, they should be glad to do that for you. They should also give you tips on how to make your vacation amazing that are specific to your family. You may even get a gift from the TA for booking your trip with them but that is TA specific. Also, if you do use a TA, you are helping someone provide for their family and most are grateful for that.