A 90-minute turn is certainly doable, and to a high standard. However, the lack of ground staff in many roles results in the frequent delays. There are often aircraft waiting several minutes to taxi the final few metres into the gate upon arrival as they wait for marshalers busy pushing back a nearby flight for example. The small delays then snowball throughout the day. I think AC among others is announcing a great deal of new growth in certain locations, but not adequately adjusting their compensation rates or working conditions to attract the new staff it needs to enable their ambitions.