Driver updates absolutely do change the picture sometimes. There is a reason I use Intel driver 4279 on my NUC with a CCFL monitor. I noted that different driver versions will change the subjective image quality as does Linux on it, and likely as does a Hackintosh OS which I haven't tested out yet. Apple released the most recent El Capitan build on July 18th, which was 9 days ago so I believe this is more of the same in terms of driver changes in the time you were away.
On Android on the device I don't love, I toggle on "disable HW overlays" and it helps. Remember to do this again if you power off or reboot as all the developer options reset to defaults.
And dating myself here but to prove that this is not a "new" problem, even firmware on a device will affect things. On a CRT Trinitron monitor, one of my graphics cards was a retail ATI Radeon 8500. I liked to play with firmware updates for a lot of things including the graphics. I ended up using an OEM Sapphire BIOS on my retail unit, because I found that on my Trinitron monitor at the refresh rates I liked to use, the picture was smoother and the text was fractionally sharper, someone else would not have noticed the difference. This was independent of the graphics driver. Motherboard GPUs also have firmware. In fact, it was noted on a Hackintosh thread that 348 NUC bios had better graphics than 246 on the Intel 6100 GPU for some unknown build of El Capitan.
Yes, there is garbage coming out on the market and is obnoxious. Try to remind yourself of one thing, there's always another software version coming, always another chipset, and you do get used to things just like you move to new places. Part of the problem is that some of us lock-in on minute things. You will never find perfection in life, good enough is a worthy aim. You'll be fine.