I've read the essay and haven't found anything debunking German & Austro-Hungarian responsibility for the start of WW1. Vrylakas argues that Germany is not solely responsible, but admits that it was Germany which decided it was a good time to start an inevitable war aimed at achieving German domination.
Russian involvement (backing up Serbia to prevent Serbia from getting invaded) was about defending its already existing sphere of influence. It seems that the only of major players (great powers) really interested in changing the existing status quo was Germany, which felt being (still) not powerful enough.
That is incorrect. Germany didn't feel the need to change the status quo at all.
Maybe you should read some papers or books about the way Serbia worked at that time. It was a convoluted mess with lots of secret societies involving both the government and the military, that where connected to lots of illegal activities outside its own borders. They even went so far to send their own soldiers on "holiday" so they could fight as "volunteers" right across the border. I guess that is where Putin got the idea from
They mastered the art of doing illegal things without anyone being able to blame them.
There were most definately parts of Austria-Hungary that were in favour of war (on a small scale). But that is also true for pretty much every country involved. All that transpired had nothing to do with anyone wanting to grow bigger, and everything to do with stupid sets of guarantees and reactions that had to happen, plus lots of coincidences going the wrong way.
Lets not forget that it were the Russian who mobilised first. They feared that Austria would try to annex Serbia, which is something the Austrians didn't even have in mind. What Germany wanted was a quick reaction, regardless of what they would choose to do. If Austria would opt for war, they should do it quickly, so it's over with before it can escalate into a large conflict. When Serbia answered the ultimatum, Wilhelm II saw no further need for action. When Austria rejected it, Germany offered the idea to take just Belgrade and stop right there, to prove to anyone that annexion was out of question. The British were very much on board with that idea. It was meant to allow everyone to save face. The Austrians would get their revenge, Serbia would remain independent, which would also please the Russians, and so on.
You simply cannot ignore the circumstances of the time. Russia mobilising automatically meant that Germany needed to mobilise, as not being mobilised if your "enemy" was, meant that you were done for (see France 1870). This in turn meant that France had to mobilise, not only to uphold their alliance with Russia, but also to react to Germany being mobilised.
It was Germany who tried to prevent this escalating any further. Wilhelm even got Nikolai to take back the order for mobilisation in an effort to cool things down. Sadly, his ministers got him to change his mind again. Germany's embassador was virtually begging the Russian foreign secretary to take back mobilisation, as he feared that the war that would follow would bring down all the monarchies (which it did).
Germany didn't declare war because that's what everyone wanted, it declared war because the only possible way to win a two-front war was holding the innitiative and taking one opponent out before the other could react. There was no possible way for Germany to wait for the war to happen. If war was inevitable, Germany needed to strike first.
Now, maybe the war could still have turned into a smaller affair if Wilhelm had told Moltke to shut it and call back the Armies that were moving into Belgium, but for some reason he couldn't. You can find similar possibilites for all the nations involved, a leader having the right idea but getting stopped by someone from the government who didn't really mind what was happening.
Simply put, attacking France through Belgium and Luxembourg had little to do with what started WW1, and everything to do with the situation at hand.
The whole mess was created by Serbian ultranationalists with connections to parts of the government. What followed was Austria-Hungary not reacting quickly enough at first and then screwing up over the longrun. It had nothing to do with Austria or Germany being interested in changing the status quo. All the bogus claims about big imperial aspirations have nothing to do with this war, they are merely ideas that popped up when the war was there and no one knew what could possibly be done after it was over. This existed on both sides as well. None of the actions prior to the start of the war fit the idea of Germany being interested in changing the status quo, on the contrary, they all oppose it.
All the big powers had more than enough chances to stop the war. They all had people who tried just that in some capacity, and some who escalated things. There is nothing which can put blame solely on one side. Trying to blame one side is simply bogus.