@Torqez asked an important question here:
This is a great question.
A counter-intel op comes to mind. Cloaking technology could impact how the map (and these kinds of tools) present this data. @Terror_of_the_Night was describing a wider map fog idea that would specifically hide who owns a planet as a galaxy setting.
Even without map fog though, a similar concept could be applied as an op cast on a planet or system instead of an empire. That way, even if it changes hands, its activity would still be hidden until the op wears off.
With either wider map fog or a more limited op, affected planets would only show ownership for the player who owns them. This would make Find Targets Planets useful once again, while also allowing players a chance to sneak into systems if they’re skilled enough.