Well, if the MATE team adheres to the “Do one thing and do it well” principle (admittedly, a DE is a combination of many things) then we should not expect a MATE based media player and we shouldn’t desire one. We’d rather see a concentration of programming efforts than a spread.
On the other hand, I doubt that the MATE team could make a good media player. This is not an indictment on the team capabilities, mind you. Rather it is a stab at a certain propensity for programmers to adopt a Not Done Here attitude that more often than not ends up with abandoned projects, subpar projects, or projects that do exist but bring nothing new or interesting to the poll of alternatives. And developing a media player that brings something new and interesting (thus a good media player) is frankly something that I need to see with my own eyes to believe.
So between an average or mediocre media player that is by MATE and no media player at all, the latter better maintains the high reputation of the DE.