But I have to admit it's hard for me to imagine Batman letting something like lack of powers prevent him from helping in a more direct way.
In this instance, the heroes have been brought to the dawn of time to fight the Anti-Monitor, who at this point is essentially a nihilistic god. The Spectre is trying to hold him and failing. Every super-being who can focus an energy blast is directing enough power at him to extinguish suns. Every being with the power of flight strength and/or invulnerability is hitting him with enough combined kinetic force to crack planets wide open. There really IS nothing Batman can add to that at that moment, and Batman is smart enough to know this, and man enough not to take it personally, that's what impresses ME here.
Now if Batman and co, heck, if Batman alone were the only hero left standing then yes, he'd be throwing everything he had at him regardless of how futile it would be (cf Nightwing being the last Titan left, but attacking Trigon with a slingshot and his explosive grenades anyway, because anything is better than nothing). Right at this point though, Batman couldn't get near enough to do any damage to the AntiMonitor anyway.