I looked at the shots of the girls playing field hockey, and it looks to me like we are seeing how that sensor performs at the very HIGH ISO level of 12,800. The images have a reasonable amount of fine detail "there"...the plaid pattern in the skirts, the weave pattern of the socks, the hair--we can see all those things, but the finest of detail is just not being resolved, I think simply due to the very elevated ISO setting. The ISO 2,000 baseball shot by comparison, which is a vastly lower ISO level, shows finer detail being resolved. If we go by ISO steps, we have 100,200,400,800,1600,3200,6400,12800. You're shooting at a full seven ISO values above 100...I personally think your camera, with straight out of camera JPEGS, is doing as well as could be expected for that size of a sensor. And the thing is, this is SOOC JPEG, right? The noise looks extremely well-controlled...no really bad noise, no speckling. I think there's probably some fine detail that has been hurt by in-camera Noise Reduction.
A few years ago, pictures shot at ISO 12,800 would've been utter rubbish...I think you're expecting too much. At smaller, on-screen sizes, the field hockey pictures look perfectly usable, with decent saturation, lovely colors,etc.. When magnified, yeah, I can see some loss of the finest detail...it's just not there...at SEVEN ISO steps above 100!
It's like you're driving at 120 MPH on some freeway stretch and remarking, "The lane divider lines are too close to one another! They look like one blurred line. What's wrong? Why do the line seem so close to one another?" Answer: it's not the lines, its the speed level! LOL!