This is the first I am hearing about this. I live in the U.S. and am not a native German speaker, though I grew up and lived in Switzerland for many years.
I don't think this is grabbing much attention outside of Germany for several reasons. I can only speak for the U.S as that is where I currently live and have experience dealing with issues of copyright and fair use (I'm not a lawyer but in my work this is a topic we are constantly engaging with). In the U.S. this kind of litigious action is very common, big companies will often go after people who they feel are infringing on their copyright (usually this takes the form of a cease and desist letter first, and if no action is taken then it can lead to further legal action), so in some ways this wouldn't really be seen as newsworthy. As you said this is primarily a German story with most discussion occurring in German so that automatically takes it out of the larger realm of discussion in the worldwide LEGO community.
Now for my opinion (I know- I know what they say about opinions). This is the first that I have looked into Thomas Panke, and I have to say that from an outsider's perspective it appears that he is at least partly pushing the "outrage" button in a move to increase engagement on his videos - this may not be outrightly intentional, just a result of seeing that videos on this topic get a lot of comments, drive up engagement and increase views, thus it becomes a bigger topic. In any event I certainly wouldn't look at the notorious youtube comment section or ratios as an indication of a greater trend. Also I have to say I'm not 100% confident in the reputability of BILD which seems to be the primary (traditional) news organization reporting on this (I admit fully I could be wrong on this as my understanding may well be out of date). As far as Bluebrixx goes, if you look into it a bit further it appears that LEGO mostly had issue with sets containing minifigures, and as they state they consider the minifig, with its precise proportions to be a trademark of LEGO. In the U.S. we would say that this is "Making a mountain out of a molehill".
As far as LEGO Sales being down in Germany, maybe in brick and mortar retail shops, but it would appear that overall, including online sales this is not the case. A quick google search brings up this info: https://www.statista.com/statistics/671661/sales-toy-market-germany/ Which indicates that LEGO along with Brandstätter lead sales in the growing toy market there. As a moc maker and designer I can fully see where people like Janke are coming from, I have plenty of gripes with the designs of some LEGO sets, but I don't see that as large enough portion of the LEGO market to make that big of a dent (and many of us AFOLS still spend $$$$$ each year on official LEGO sets despite our misgivings). Granted, again, I will admit I am not that familiar with the German LEGO afol community.
If you've made it this far thanks for reading lol. If this is a topic you are interested in you can see more here https://www.lego.com/en-us/legal/notices-and-policies/fair-play/ where LEGO goes over what they consider copyright infringement and what they don't in great detail - and you can see where they may have issue with people like Janke and Bluebrixx, whether those objections are legal or not, well that is up to the courts to decide...