Resources feel significantly less impactful despite having more of an effect than Civ 6. Part of this is due to the removal of bottlenecks in unit production due to not having enough of something (ie Oil, Niter), which while alleviating some frustration also removes a lot of strategic depth to the game.
Especially with the immediate gain of resources through trading with another city, they just seem almost too plentiful now. In Civ 6 you'd often be forced to go to war based on the differences in resources between you and your neighbours, or settling strategic locations to gain access to valuable resources. But it doesn't feel like it matters now. It removes a significant level of dynamism from the game
Resources should be more impactful drivers of settling and war. Add value to pursuing stuff like Niter or Oil again, maybe through a softer bottleneck than Civ 6 (ie a max cap on a unit based on number of improved ______). Nuclear weapons especially need the reintroduction of uranium, feels to easy for anyone to build them.
Strategic resources should require a certain level of relations to be obtained through Merchants (could have new civ that bypasses this). Some resources like uranium should be obtainable through espionage.
Resources should be clustered more outside of just terrain (IE everyone doesn't have the same things, also drives trade)
Add global effects to more mundane resources that offer a limited but significant boost to your civilization, including new world treasure resources.
Changing resources in this manner will increase their perceived and actual impact to your empire, adding a dynamic level to trade, colonization, and wars. This will add much needed depth to the modern age.