As much as I have had many great experiences with the S5; sadly, you are sharing many of the thoughts that I have shared. Particularly after the dismal deployment of Ultimaker Cura 3.5.
Like you, I purchase what was solicited as a long term tested commercial printer that was to be pert near plug and play and paid; comparatively speaking; a premium for it however, I too feel as if I am smack dab in the middle of a development curve; this curve being Ultimaker’s.
And yet unlike you, I still hold out hope that they will deliver as promised as such I openly expresss my thoughts, share my concerns, implement work arounds as needed, assist others when I can, and throughout; I remain support of the Ultimaker printer because; I think it is a good product supported directly and indirectly by many many folks that care.
My last comment included “care” which is pivotal to how I feel today.
In my opinion whether an open source environment or not the proverbial buck begins and ends with the core Ultimaker team.
You mention how responsibly was shifted as if to say; not/no longer our responsibility and yet it is and soliciting products into and for the commercial arena carries with it responsiblies far beyond those of the hobbiest and enthusiasts. Now this in no way diminishes anyone’s value but rather the associated risk and cost burden is different between the groups.
In closing, I too have had my moments of frustration as such truly understand where you are coming from and your ever increasing frustration. For examples; I too was told after the fact that there was no easy way to implement static IP, experience random issues with the printer that akin to a ghost, come and go, firmware issues, Ultimaker Cura 3.5 deplyment issues, and yet I would encourage you to do as I have and take a deep breath and let the process become mechanical rather than emotional because the later will prove to be a fruitless exercise in futility.
I will restate; I think that the Ultimaker team want to have the best printer line in the marketplace and because they care I believe they will do it. If I did not I would have boxed the S5 up and shipped it back because at this moment; just like you, it is “not” all that I was promised.