Now I started to photograph with digital cameras.
Now I notice that I cannot judge the technical quality and differences of my photos on the computer at the moment. That's my problem right now.
In this respect I am looking for clues on how I can make progress.
Being constructive, I would say that's because
all of the systems on your list are extremely capable in a very wide range of shooting situations.
More so than in the days of film, in my opinion. There's just not so much difference between even an APS-C sensor and a "mini" medium format sensor. It's not like 35mm vs. large format from film days.
I'd say if you can't judge the quality and differences on your computer and you intend to look at the photographs you take on your computer, all of these systems will do just fine for you. Indeed, you might even find that a micro 43 or a cheap Canon dSLR would do the job for you today.
If you can't tell on screen, maybe you can tell in prints- as Jim suggests, make some and see. Especially if print will be your final output destination for any significant fraction of your work.
Looking at the RAW files will tell you nothing about how the camera will perform for your photographic tasks, for your workflow, for the subjects you shoot, in the lighting conditions you shoot in, for the RAW processor you favour and the look you are trying to achieve.
Hire each system for a day and try them out. It's by far the best way to figure out which system works for you. A day's rental is peanuts compared with investment in a new system, especially if you're going to be buying a bunch of top-flight lenses.
Try processing the files from those shoot days yourself, the way you're going to be doing it if you buy one, and see what you think of results. Weigh that against what you thought of the shooting ergonomics, the shooting envelope (how capable the system was in the range of shooting situations you usually favour), and not least the price.
In many ways I'd say the choice of RAW processor is as important as the choice of sensor. I personally find it much easier to get results I like in Capture One, Phocus and Aperture than in Lightroom or DXO; you might find the opposite.
If you do a lot of shooting in remote locations, you might find that the startling weight advantage, long battery life and general robustness makes the Panasonics or Olympus micro four thirds options viable. I have printed them to 36"x24" but I can tell the difference between those and a full frame Sony A7RII/III. So much so that I never take the Panasonic into the mountains any more. But printing to smaller sizes they're just fine.
If you always shoot near the car or in the studio, and like the methodical and slow way of shooting, maybe the Hasselblad/Phase is more your style. Then again, the focussing capabilities of a Canon 1DX Mark II or eye focus on a Sony are almost supernatural- if that's important, you owe it to yourself to try them out.
All modern systems are good enough.
None are perfect.
Hire and find out what strengths and weaknesses are important to you.
Cheers, Hywel