The reason I raise the subject of DXB flight congestion is that a few years ago my son was flying QR J ARN DOH DXB (in the days before the UAE threw their toys out of the pram). As I invariably do I was tracking his progress on FR24. His ARN DOH flight landed, without delay, at approx 2300hrs. His DOH DXB flight (< 250 miles) departed DOH just after midnight and made its way towards DXB, however the aircraft made no fewer than five circuits of a holding pattern offshore before being able to land at DXB - it appears that many other aircraft suffered similar holding pattern delays. What could/should have been a 30-45 minute flight turned into 75+ minutes in the air.
I’ve never seen much in the way of delays for aircraft waiting to land at DOH - although admittedly there can be some queues for take-off at peak times.