I also just purchased a '16 ZX10R and I'll be the first to admit the engine probably has the softest low-end of all literbikes I've ridden. I think a good deal of this has to do with the extremely tall 1st gear, but I believe the engine is a little soft as well and doesn't have the greatest fueling down low.
For any Gen 4 or Gen 5, I believe the most bang for your buck would be to flashtune the ECU and unlock an extra easy 10+hp with no other modifications and it will help bring back some of that low end and give you a healthy boost in the mid, and a very healthy bump up top. This bike really needs to be wound out!
Otherwise, I think the handling could be partly to blame. The front end is incredible and the bike tracks very smoothly yet quickly, but also very stable.
You could try dropping a tooth in the front sprocket (-1) or going up in the rear (+2) or both if you want a substantial change. Note your top speed and cruising RPM's will change however.