Actually, it's not clear to me if it is too many object that GSX is creating in and of itself, but it seems to be a combination of things that create too many objects (AIGTC, GSX, other airport life, etc) such that some sort of sim limit is being hit.
Of course it's a combination, if there's a hard limit on the number of objects that can be created through, no single add-on is "responsible", if the limit is, for example, 1000 objects, it's not obviously GSX's fault if other add-ons already created 500 by themselves, it's up to the user to limit the number of objects created overall, if the add-on allows it.
GSX creates only the objects around the airplane, the highest number are probably the passengers, depending of course on your Passenger Density slider so, if you have a program that does AI injection, you might not way to use the "Insane" setting, which is not default, and it's called "Insane" for a reason.
Those are the ones created by Simconnect. Now, somebody trying to test this, might be mislead assuming GSX creates more objects through Simconnect that it really does, because one might see GSX-related objects names in the scene. However, for the precise reason of not risking breaking Simconnect, GSX use extensively the new "Attach" feature, which allows to have more objects on the scenery WITHOUT having to make a separate Simconnect call for each one.
Example, a Baggage cart can contain up to 11 bags so, with 3 carts per loader and 2 loaders working at the same time, if we didn't use the Attach feature, we would have made 66 + 6 = 72 Simconnect calls. Instead, we only do 6 calls for the carts, because the carts come with the bags already attached and controlled by a visibility variables. Even the drivers are attached to the vehicles this way so, instead of doing 2 calls (one for the vehicle and one for the driver), we only make one. Same the Passenger Bus, when it's full it can contain 47 passengers but, instead of making 48 Simconnect calls, we only make 1 for the Bus and the sim will automatically attach passengers to it.
This feature came in SU9, so we use the latest method to keep the number of Simconnect calls as low as possible.