Hi Josh and welcome to the game and forums. Fellow Mac user as well.
That would in game terms be classed as a big airport. I’ve a 27" 5K iMac, top spec as well. I get to about 5K PAX and the game does indeed start to have noticeable issues like that. Having said that though, push 2K PAX was impossible only a short while ago.
The Dev’s are consistently looking to improve performance and have made major gains and they keep coming. They have just started to look at a new way of rendering PAX as well that seems promising.
Have a read of the latest Dev Log too for a little more information as well.