As I know the identity of southern duel and recent history perhaps his rant is not unexpected.
I do agree with him regarding the current taxiway situation but he probably doesn't know that this should be resolved fairly soon. Runway occupancy hardly seems a problem at the current flow rates and even the climb path obstacles on 24 don't actually cause much operational difficulty and SEN is not alone in having that situation.
As for his criticism of aircraft handling, I don't see how SEN's very good on-time departure record supports that contention and neither would an airport win the Which? Best Airport award two years running as poor handling would be bound to feed through to passenger dissatisfaction. I think there may have been staff reductions this year in some areas but again SEN is not alone in trying to keep costs down. I use SEN quite frequently and am also often there to attends meetings and have never seen sloppy, inefficient handling or whatever deficiencies he may be suggesting.
It all rather smacks of sour grapes to me.