Key Object Performance Issues
When aligning to a complex key object, the performance is terrible. When I click on a complex object (say, a group of complex paths or illustrations) to set it as the key object, it lags for several seconds after clicking before I can click an alignment tool. The length of the lag depends on how complex the key object is. This behavior never occurred in prior versions of illustrator. Very annoying.

Please get in touch with us at any of the other support channels – https://helpx.adobe.com/support.html . Since this is not a generic issue that we can reproduce at our end, we will need someone to look into your machine to figure out what is going on here.
Warm Regards,
Ashutosh Chaturvedi | Sr. Quality Engineering Manager – Illustrator