The biggest immediate bottleneck, so we are told, is the number of airport workers. HK is importing more to deal with this. Without more workers it's been difficult/expensive to restart flights for many airlines because of the need for baggage handling, etc. Demand isn't the biggest problem: CX flights have been running fairly full and fares are sky high as a result of the supply/demand disparity.

Some of the difficulties reconnecting are political, and not just HK politics - Russian airlines and Russian airspace also continue to be issues, particularly for US airlines flying from the East Coast.