My default/typical search criteria is aa+ and f ~bc=b; -overnights. I'm typically searching from 1 airport to 5 (or fewer) airports. With old matrix, I would get a whole host of options, typically 100. With new matrix, I get a maximum of 10, ever. I then narrow down by specifying connecting airports or specific flight numbers.
I've had problems with aa fares on oldmatrix ever since aa started trying to play games with the fare classes they were willing to distribute to OTAs and TAs when vasa raju was ill-fatedly trying to force everyone to book direct. Other airlines are fine; I don't think this is an oldmatrix/newmatrix issue but rather the distribution system that matrix is pulling from vs google flights because of aa's distribution nonsense.