The CIS really could have won the Clone Wars without Darth Sidious and Dooku's schemes to eternalize the war and give more powers to Sidious so he could become emperor in the end. The CIS had a vaster army and fleet, their military industry was far larger and more widespread than the Republic making it extremely difficult to neutralize it while the production of clones, ships and land vehicules were centered on far less numerous planets such as Kamino for the production of clone soldiers and specialized units, Rothanna for the production of military vehicules and Kuat for the production of Star Destroyers and other heavy ships.
Which means that had the separatists not being held back by the Sith they could have maimed the Republic's war effort by frequently targeting these worlds which would have done far more damage to the Great Army of the Republic that the taking of an equivalent or even superior number of separatist industrial worlds.
Also a good portion of the Droid Army was kept in reserve on Dooku's orders and had these reserves been unleashed the CIS could have overflew the Republic on several fronts. Also the Sith also sacrificied several of the separatist's best tactical and strategic minds such as Sev'rance Tann, Merai or Pors Tonith. And when the separatists produced a droid or ship class that could have been sufficient enough to give the edge to the CIS Sidious would secretly give away the plans or locations of production of these droids or ships as seen with the CB3 Cortosis Droid :