Well the age of the Doc is not really a problem; we've had one middle aged and two young ones since it returned, which is not drastically different from before- and Moffat was in fact casting for an older Doctor but got captivated by Matt Smith.
But having such similar companion dynamics really does wear thin on me. They don't seem to be changing it up at all- if they are going to keep on having them as contemporary Earth companions, they need to mix that up.
To be fair on RTD, Martha was an educated middle-class type where Rose was working class (though one gets the feeling some writers just gave her the same dialogue Rose would have got), and subsequently Donna was indeed very different from pretty much any Who companion there had ever been. The dynamic there changed constantly, even within the contemporary setting.
We'll see what this new girl is like but... hmm, I am suspicious.