The original Schlieffen Plan had long since been abandoned because the original Schlieffen Plan was a pipe dream. Even further the Schlieffen Plan did not call for an attack on Paris but an encirclement of the French army. While since its original drafting the planning would bounce erratically between attacking Paris or continuing the drive in event of war eventually it was settled on to play it by ear. In the context of the war it was decided upon to continue the encirclement.

In hindsight no matter what they chose to do it did not matter; a victory was not going to be achieved without massive timeline alterations in September 1914. Honestly from my reading it was the preferred option as well. At its core, both the original and modified, the Schlieffen Plan was a gamble. It was a gamble that the German army could mobilize faster and strike faster than the French and through overwhelming strength force capitulation. This had to be done first and foremost by neutralizing their army and, like 1871, would have to be done by encircling them and breaking them. In the original iteration of the plan this meant letting the French invade Bavaria and then swinging around them and hitting them from all sides. In the modified Schlieffen Plan this meant pinning them on the border bleeding them in attrition while they were hit from all sides similarly.

Ultimately an attack on Paris wasn't a decisive attack it would have been a slogged down siege. A siege against some of the most formidable fortresses in Europe and, unlike at Liege, not massively outnumbered. In fact those forces would have twice the artillery of the 1st and 2nd Armies who were bled dry to 50-60% combat strength on top of everything else. It would look far more like Verdun than it would Liege and did not suit the rapid assault the Germans not only hoped for but needed. Ultimately it was a gamble -- they gambled Paris would be empty, they gambled the French were truly routing and not strategically withdrawing waiting for prime opportunity (as they were), they gambled the second they invaded a power who was making no clear moves to get involved in yet another distant Balkan crisis.

See these prior answers for further reading:

• How did Germany quickly defeat France in the Franco-Prussian War and World War II, but not in World War I?

• In WWI, why didn't the Germans simply go around the Belgian & French forts?

Ultimately, as my second post mentions, for one last reiteration, Germany was in a fundamentally unwinnable position at this point. The offensive had failed. They could not bypass Paris because it gave their side but they could not siege Paris because, well, they did not have the men to take it nor did they have the time. It was a lose/lose situation. So they gambled on the option of pursuing the Armies as at least then if Paris was abandoned/not nearly as packed to the brim with soldiers they had a chance.