Exploration is required regardless. You need to discover your surroundings literally every game. You explore to meet neighbors, find expand locations, meet CS (not for first-to-meet, but to map out which are in the game/which you want to invest in), understand terrain layout, strategic resources, kill barbs, etc. Giving people the equivalent of a free civic policy or a free monument for getting lucky while doing so isn't reasonable to me.
That doesn't change the fact that you can do it at different speeds. You can explore early, or late, you can explore fast, or slow.
You are rewarded for exploring early and fast - you are not rewarded for "no reason".
That's like saying people who beeline a specific wonder tech and then are able to beat the other civs to their construction got those wonders for "no reason". The reason is that they took specific action to get there first. No one starts with a scout in civ6 and you never
have to build one. The movement rules in this game make exploring a lot slower than previous games so you can either make exploration a priority or you can not.
If you don't, you're very likely going to lose out on most goody-huts and all of the CS bonuses.
Consider this; You having 1 envoy with a Industrial CS gives you +2 production in the capital. Eventually, every other opponent has the potential to get that, and all of the other bonuses aside from the competition for suzerainty. So by removing this one city-state from the game you, as the player, are losing +2 production (just focusing on this first bonus right now) and yet you're pulling a potential 14 production across the entire world out of the game (standard 8 civs).
If this were civ5 and the bonuses were very specific to the person that controls the city-states, I may agree with you. But the fact that the
bulk of the worth of CS is achievable by any civ
regardless of suzerainty - I call fowl on the balance implications of removing them from the game. Going back to the industrial CS, the total net worth of +2 production to cap and +4 production to all industrial districts is available to
anyone with 6 envoys.
To say nothing of the fact that there's more than 1 city-state in game.
You're cheating your opponents by leaving them out.