So with huge military ranks to fight the ground battle, as well as a pretty fantastic team of six heroes with powers and tactics beyond compare, it’s fair to say that the Justice League would have a handle on beating Thanos; especially with The Flash being able to run the time travel play if need be.
Even in that respect, without the powers of the six members of the Justice League put together, the fight is pretty much lost.
Though it also helps that the armies of both Wonder Woman and Aquaman would have the numbers to help soften up Thanos and his own forces.