You can help win the objectives indirectly.There is absolutely nothing favorable to players who step away from the objectives.
Fallen Fighters can be a good example.
As the Axis player the key to success (and by that I mean capture and holding of C) is not the left side (although control there helps) but the right side. To be more specific - Germans have to hold Soviet tunnel on the right side, from there they can reinforce C and, more importantly, prevent Soviets from getting into C with ease.
Soviets are much more safer there as their backs are covered by their own MG's, marksmen and sharpshooters from A. Germans are more exposed. Point is, with Soviet tunnel held by a handful of Germans the Red Army has to expose itself to German MG's, marksmen and sharpshooters firing from E, making capture and holding of C much harder for Soviets and much easier for the Germans.
We won that map, as the Axis team, exactly because we held that tunnel. It isn't direct objective but it's vital for the success as a whole (it's also easier to reinforce right side when you control it and find cover in both tunnels if artillery goes down, plus there is no danger of enemy fire, or at least not as high as across the Park).
Another indirect help is hold off left side (from the German perspective) as then squad leaders can put smoke to reach their own tunnel without fear of being killed on the way and help to capture C from another direction.
In short - you not only defend the objective by being there, you also defend it by preventing the enemy from being somewhere else.