Except you don’t always have that information. You don’t always have vision of all cities in a civ’s empire to count up their population. You can’t always see all their wonder tiles, and some wonders don’t even have graphics to see. You can only get an incomplete picture of the size/strength/wealth of an empire, and spies give you the precise information to resolve that into an accurate portrayal of the other civ.
You know the placement of civs, but spies give you the exact score. You know that the civ with the biggest

per turn has a GDP of 100,000, but you don’t know who that is unless you have a spy on them.
Any criticism of the spies giving you information that you could impute yourself from map data either implies one of two things:
1. that you are willing to do the work to count up tiles and work off those estimates. In that case this system rewards you, because you could put that effort in and just use your spies for CS rigging, and try to play optimally that way
2. That you aren’t even willing to touch the spy mechanic even if it is needed for basic fact-finding. In which case you should just turn the system off.
3. You think that players should be given everything for free. In that case you should just play with InfoAddict
Otherwise, what you are actually arguing is that you will not use spies in this system… because you refuse to help yourself with the tools available to you. Its a claim that you won’t be able to access information you never tried to get in the first place. That’s like demanding that we make roofs lower so we can climb on top of them without the use of the ladders,
while holding a ladder.