But, AFAIK, you don't get a Diplomatic Modifier for offering a favorable Deal for the other Player like in Civ6, so it doesn't make sense to offer more, less is always the optimal choice, which makes sense there, but not in Civ6. But you also still have to visit each Leader to know the best offer you can get for your Marble, there is no Panel where you have everything listed and sorted, which is what Quick Deals does.
I also wanted to partially correct myself here, bc I forgot about Total war 3 Kingdoms, which has a Quick Deals option, and which seems to be the inspiration for the Mod for Civ6. But only "partially" bc even in this Game that offers this Option, which many People seem to perceive as the best way to make Deals, still has it as an Option, not as the main way to enact Deals. Why? Bc even though the Devs came up with such a Tool, they still know that the best way to make Deals is through bargaining. Why? Bc with bargaining you can customize the Deal however you want, add more Items to offer if you don't have enough Gold for the Great Work you want from the other Player, or even close more deals in 1 Go. You can't do that with Quick Deals. Bc that's what it is, a quick way to get the best Price for a specific Item or Items, with the Cost mostly paid with 1 Resource (Gold). In other words, each has its purpose, its pros and cons. None should be the only way to make Deals.
That being said, the Deals (and also Diplomacy as a whole) in Total war 3 Kingdoms are better designed than Civ6. You can easily see at a glance if the other Player likes your Offer, and any change in Offer or Demand is immediately reflected in the UI at the Bottom whether the other Player likes it or not, makes bargaining much easier. And the "Make This Work" is also a life saver if you don't want to negotiate yourself. We do have the "Make this Deal more equitable" in Civ6, but I'm not sure it works as intended tbh.