Atheon cannot be tracked in the same fashion as Broly. Remember how hard it was for them to find and defeat the androids? They gave off no power signature. Broly radiated energy at pretty much all times after he killed his dad. And I'm not denying goku can go between realms (which is still different from time travel, goku doesn't have the same travel ability as Dr who's TARDIS) but in dragon ball z there's only 3 or 4 that are mentioned in comparison to an infinite number of instances in time inside the vault of glass, plus like I said goku wouldn't know where he is and or where he needed to go to even think about teleporting back on his own. But even if through some stupid low probability that he was able to teleport back, did he bring the relic? No? Did he kill the oracles? Hm. Looks like hes blind and well on his way to being lost in time.