Modern mixing methods involves more and more sidechain, often using plugins such as LFOTool or VolumeShaper ... This trick is quite old, yet not a single DAW thought of implementing straight into the DAW code, instead we have to rely on third party plugins. This makes things too complicated for what a simple thing. I personnally use two sidechain tracks = one for kick and one for snare. Everything goes through it, except the kick and snare of course.
When exporting stems, you have to make sure you select the tracks with the sidechain on it, or else you can restart all over again.... And believe me no matter how hard i try to remind me of doing it, i always forgot a few times....
Please, Logic Pro programmers, be the first to integrate a full fledged, simple to use, super clean and export friendly sidechain feature right into logic pro ! It's about time someone does it !