An unorganized army and an already in-stable political situation would definitely lead to crisis if the German pushed in quickly against an unprepared army like they did during ww2. I doubt that France would wanna leave their defensive positions at the border so Russia would be borderline alone (Correct me if I’m wrong about any of this which I assume I am).
The Schlieffen Plan was based on the (accurate) assumption that France would be able to mobilize much faster than Russia. France was a simply geographically smaller country with a better infrastructure, which made mobilization much easier for the French Army than for the Russian Army. As a consequence, German war planning focused on rapidly defeating France before Russia had time to mobilize and attack Germany on its eastern flank. If I’m correct (I can check my sources this evening, but I’m on mobile right now), full Russian mobilization was expected to take about 6 weeks.
If the Germans had directed their initial efforts towards capturing Moscow and knocking the Tsar out of the war, they would have had to either leave the west undefended and face an invasion by France and her allies unopposed, or divert enough troops to defend the west and attack in the east, which was an acknowledged unsustainable plan — hence the creation of the Schlieffen plan in the first place.