Actually, I have moved away from still photography and for 4K video I use a Lumix G85, a Sony a6400 and a Sony AX-53 (camcorder). My Xperia 10 iii also does very low quality 4K video, but I doubt that I would use it that way unless someone specifically wanted something done that way. I still use my GF3 as a knock-about camera, but it has been pushed low on my choice list.
I wondered why the GF3 did not make better pictures. I was especially disappointed with the results from raw files. I had heard that the GF5 made better pictures despite having essentially the same resolution. Eventually, I simply moved upward through various bodies. But I occasionally wondered why the GF3 was so disappointing.
Eventually it dawned on my what was probably happening. I believe that the GF3 is probably applying "chroma sub-sampling" and specifically YUV 4:2:0, just like most common video frames. I never did a formal analysis, but that is what the files look like. It must be happening very early in the imaging system. it might be right in the sensor's controller, so that there is no way to get around it. It should be possible to a check this by analyzing images pixel by pixel (seeing if groups of pixels have the same colour shading but differ in illumination), but at this point I am not that interested in doing the work. If I am right about this, then the GF5 might just be applying YUV 4:2:2 (which would be sort of "one step better") or it might be eliminating the chroma sub-sampling completely, which would be what most stills cameras would be doing. Also, if I am right about this, then pictures in "monochrome" should look as good as done on better cameras (at the same resolution, within 8-bit limits. But that does not really help me because after years of doing monochrome photography (real paper and chemicals), I just do not want to do monochrome anymore.