Like wise large loco such easyJet, Ryanair, Norwegian often operate from busier airports such as LGW, STN its a very different situation from LBA, EMA, NCL, BPL or even Manchester.
I would put LGW and MAN in the same category, both have in excess of 20 million passengers, both are ACL Level 3 co-ordinated airports.
Stansted is a doddle compared to Manchester, it may be single runway but its taxiway layout is much less likely to cause delays.
Manchester has a layout which was not designed, it evolved.
On a summers morning in Manchester it can be carnage.
It is a wonder it works as well as it does.
As an aside STN is also ACL level 3, despite it only having about 17 million passengers.