Based on what I have seen, rather than the marketing materials, I regard the GH5S as a great cam for event and wedding shooters who are always running around with monopods, little gimbals and little lenses. However, in my workflow, I don't want a b-cam that doesn't have IBIS. I have enough heavy gear and manual glass to deal with without the headaches of a rig for a stills body cam.
Whether the image quality is an improvement over the GH5 outside of low light, or actually a little worse...remains to be seen.
In terms of what is good for low budget cinematographers, I suppose if the highlight roll off is as good as is claimed and the motion cadence is improved...the GH5S may be a contender over blackmagic purely for ease of use and reliability.
I definitely don't think that the GH5S release is a 'fail' in any way. It has it's place and people on forums have been loving the whole 'low light monster' meme since the A7S came out. I want Panasonic to continue to innovate.