The tram is a lot better than it was just 5-6 years ago, but on matchdays I avoid the section Piccadilly to Etihad.
At least there isnt tram works every City weekend like there was a few years back, but none on United match days.
They are restricted by number of trams, how many they can have on a line at one time and I beleive drivers have to have extra training for double trams (citation needed) and because everything hits the city centre bottle neck that reduces possible capacity on the Ashton line.
It's not a lot better over in Trafford on Match Days and they have 3 fully functional lines and approx 5 or 6 walkable stops within a mile.