Painter Holiday.....

I have worked as a high-end Painter for 25+ years; and absolutely despise caulk. If it is done right, there is almost never a need for caulk. There isnt a single ounce of caulk in my entire house, which I reno´d myself - except a bead of clear silicone around the exterior frames of north-face windows - where we can get side-winder downpours from the nor-easters.

If someone asked me to fix that nightmare above I would say - get someone else! Not touching it. Or perhaps, do you have fire-insurance?

To be fair, even with initial tight joints, say, with trim around a window or door, with the lousy grade of wood they use nowadays - when you come in to do a repaint whatever-years-later there are going to be some gaps at the miters due to shrinkage. I would never use caulk to prep those in that case, my go-to fix would be/is old-school linseed-oil base glazing compound.
Another thing I would do, to minimize shrinkage of new wood, is to prime the backside of any trim (before it gets cut and installed) with an oil-base primer. Of course, this is only suitable for wood that will be painted, and would add to cost which some clients may not accept.