To me, "struggling to hear dialogue" (what the TS said) sounds like a truncated centre channel, but you're right that I shouldn't have assumed that your statement was also predicated on this statement.
Still, we cannot preclude the possibility of a truncated centre channel. Also "struggling to hear dialogue" sounds different to me than "dialogue doesn't sound as forward". I've never had problems understanding the dialogue in a movie, even when on stereo, except when it was supposed to be difficult to understand, e.g. when the people in the movie are on a small boat in a heavy lightening storm shouting towards each other. Just for fun, could you point me to a particular scene in a movie where dialogue is difficult to understand in a 2.0 or 2.1 setup? I'll set my amp to 2.1 and give it a swing.
In any case, if what your assumption is right maybe TS could try to apply DRC (never thought I'd say this). If my assumption is right TS should just enable proper downmixing.