we have a quite large project tree here - consisting of one main .pro file which then contains several subdir projects and so on (around 400 .pro files).

The problem that we are facing is that when loading our project, the GUI of QtCreator freezes until the project has been loaded.

Because of the size of the project you have to stare for about a minute or two on a non-responsive screen.
This leads to the wrong thinking that Creator has crashed - and several fellow developers just kill the app and try again.

You can try this for yourself when loading the QtCreator sources: QtCreator is unresponsive as long as the project is beeing loaded.