I didn't watch this vid when Black Phoenix first posted it, but I wish I had. Points to the YT creator for a Great Ironic title. That is some of the worst containment work I've ever seen, and I have to deal with stoned/disinterested apprentices. If I did work like that, I'd be fired pretty damn fast.
For the apprentices, I can feel you- and BTW, YMMD with that quote ;-)
But honestly, I have seen worse from some professional companies that were regarded as good quality in the area where they were providing services...
I admit that I have only given it a quick glance, and spotted one or two Wago where it probably should not be in the first place, but the main setup from the approach looked reasonable. In the "Brüstungskanal" he uses pluggable outlets that are able to be daisy-chained, which is usually some expensive stuff from special manufacturers.
In the "Abzweigdosen" (connection joint boxes) the usage of Wago ist normal in germany and in fact the preferred way of doing it- I would have to look up if german code demands connectors like this.
And because those boxes are available for inspection at anytime, it conforms to code regarding final electrical installation testing (isolation/grounding), where it says that you have to visually inspect those joints for signs of overload/trouble. In Germany usually mandated for commercial objects every 4 years. Ok, he does not show that the installation is tested after installation ;-)
In contrast, the use of wire nuts is frowned upon in germany- maybe some stuff that seems strange is due to differences in country and code?