There are several reasons why decommissioning the High Seas Fleet wouldn't have helped the German Army. The fleet played an important strategic role, as a defense, a deterrent and a threat. Removing it would have given the Allies a much greater freedom of movement and action, that would likely have outweighed any benefit seen on the Western Front.

Firstly, the High Seas Fleet was a major part in the defense of Germany's north-western coast. Removing the fleet would have required many of the sailors and weaponry be retained to serve in the same role. Had this capability not been maintained, the British could have landed troops, or bombarded coastal targets with impunity. Off the Belgian coast, British monitors and amphibious forces, unchallenged by German warships, were able to effectively suppress the U-boat bases at Zebrugge and Ostend. The thought of this happening to German coastal bases and towns quite effectively deterred any attempt at decommissioning the High Seas Fleet.

The High Seas Fleet also had several important strategic roles, beyond simply defending the coastline. It prevented the British from shipping supplies to Russia through the Baltic. Without it, the British could have supported the Russians, keeping them in the war. Any gains from removing the HSF would have had to be diverted to the Eastern Front, rather than anywhere else. It acted as a threat to the British blockade of Germany. By doing so, the British had to maintain a massive fleet, to prevent against any action by the HSF. The ships could have been very useful elsewhere, but had to sit around in the North Sea, doing nothing much. In addition, the HSF made several attempts at drawing out the British fleet and defeating it in detail, even after Jutland. As long as the fleet was afloat, there was still a chance that they might be able to do it - in 1918 they only missed out on sinking a couple of British battleships because their intelligence service got the day of sailing wrong.