If you wanted the 5D MK IV joystick, yes the 6D II does suck
If you're annoyed that you keep hitting metering mode button rather than ISO, yes, the 6D II does suck
If you expected better image quality than the top of the line Canon bodies yes the 6D II does suck
If you expected amazing innovation from Canon then yes, the 6D II does suck
If you expected amazing improvement in DR then yes, the 6D II does suck
If you expected no work as a photographer to produce beautiful images then the 6D II does suck
If you paid full retail then yes, the 6D II does suck
If you did your research before purchasing you would know its strengths and weaknesses, and if any of them is an issue for you and you did purchase then yeah, you made a mistake. The rest of us got another fine Canon camera that will do the job it was intended for. I liked the original 6D just fine (and remember the same whiny posts about it too). I prefer my 5D III over the 6D II, I like the 5D IV best. But I can still do my job with any of them, because
Choose your tools based on what you need to do, not some lame-arsed clickbait article.
I agree with your points above, but that's a lot of caveats to worry about. It's almost unheard of for a technology company to bring out a model that isn't an improvement, especially priced at the 6D II level. The 6D II is a capable camera, however it represents the frustration that Canon compromised so much on features to protect the 5D4, particularly given the competition. Either that or they are really behind in sensor technology.
If you have good light and don't use super shallow DOF then it doesn't matter so much what camera you use. In fact the flip screen and GPS on the 6D II make it a great travel camera.
If Canon had made the 6D II with about the same autofocus points as the 5D3 (5 year old camera) and an incrementally improved DR, I would probably have gone for it. However the 5D3 was frustrating me, and I was forced to consider the 5D4 to get some features that are valuable to me (increase DR, better AF), but by switching to the a7RIII I get more that's valuable to me (Eye AF, silent shooting, even better DR). Enough for me to stomach extra cost of changing systems, although I am keeping some Canon glass to use adapted.
If these features don't matter to you, or you want a more robust and weather proof body, the a7RIII is probably not worth it. I didn't care if was mirrorless or not, I just want a better tool to take pictures with. I wish Canon had made it, I would have saved some money.