Code editing is unresponsive

There is definitely something wrong with the efficiency of the code editor, it got worse from versions to versions, even after having disabled background indexing.

The on-the-fly compilation system makes code editing very unresponsive when a file containing complex code is edited. I suspect the associated threads are not halted immediatly when a new character is typed in and it slows down the editing altogether. That or the processing of that input is delayed because the compiling thread is taking too much ressources.
Anyway, this makes the code writing experience so annoying that I have been seriously considering migrating to another IDE but converting .pro into cmake is a pain in the back.

Reproducer : 
Open a large .hpp file from boost 
Try to edit the code 

Intel(R) Core(TM) i5-8300H CPU @ 2.30GHz

Regards