i feel that inclines indeed tax the shoulders a lot but it also DOES shift the focus away from the lower chest to the upper chest.
This can be a good or a bad thing....
Flat bench jedis will argue that this is a bad thing because the sheer heavier weight used for the flat bench create a spillover to the upper chest that they feel practically equals the amount of stress placed upon the upper fibers using incline benches. and even if EMG studies would show that inclines stress the upper chest more, the overall net mass gain in chest would be better from the flat bench they argue.....
I feel they have indeed some points but what i think what's truely important limiting or suporting factor in upper chest development is the strength in your front delts. I think that people wth favourable strong front delts, people should definately do incline as the delts will not hold them back so they can create more substantial stress on upper chest than the spillover from the flat bench could. People with relatively weak front delts are limited in the weight they can incline bench hench the spillover from flat benches might actually EQUAL or MORE (!) than they could get from the incline bench.
Moral of the story get your front delts and your rotators up to par so you can profit from incline work.
Here is a no brainer chest workout using 2 exercises only:
12-10-8-6 low incline dumbell press
12-10-8-6 low decline dumbell press
4*10 low incline dumbell press
4*10 low decline dumbell press
That's it !