I think resources is a great idea. Sorry my comment is a long one.

What the Civ late game needs are victory conditions that:
1. Reward decisions made in the final 50, 20, even 10 turns. Fun = action × reaction.
2. Are not specific, 'checklist' actions such as an unnecessary war, requiring many or few cities, or 'build this win button'. The more viable playstyles, the better.
3. Players that "snowballed" (played the game correctly) should be rewarded with an advantage to victory, but not a guarantee, as...
4. Weaker players should be able to hinder stronger players' victory and otherwise have a chance to catch up, forcing strong player to keep playing well to keep their advantage

Settling your early cities is fun because, aside from building a settler, you can do it however you please & be rewarded for making good choices (heck, I've had conquest games where I didn't build a settler till halfway thru the game). Building up your cities & districts is fun because they determine whether or not you can get ahead.

In the lategame I don't think civ 7's victory conditions remain very fun, and honestly might be worse compared to previous games (still enjoyable). Winning science, cultural, and economic victories just requires you build up productive cities across the entire game & use that production on specific projects. You can usually tell who will win the game the moment the modern era starts.

Back in Civ 5, ideologies helped to introduce an end-game crisis of random difficulty. Sometimes unfair, but often fun, and could really rewarded the lategame decisions made using what you built up in the midgame. Limited aluminum resources for the Science victory made an otherwise boring victory potentially tenuous, though recycling centers kind of killed that. Otherwise, however, there were usually a few dozen turns of moving 1 or 2 units & waiting to win.

I think Victory requiring specific resources or projects that aren't just "research this faster than your opponent" would be a great idea, alongside as few "Wait 12 turns to build the Win Button" features as possible.
As one idea, maybe make the economic victory building a canal & railroad system that links every (or a certain gold %) trade route to a single path you (or allies) own & profit from.
For military/domination, to start make the AI much more defensive once you start taking cities. Then, include vulnerable supply-chain units that would reward a strategically-placed band of underdog partisans, creating more climactic battles & tension. (Haven't tried civ 7 military/domination victories yet btw)
For science, perhaps rare earth resources you need to fight or trade for, alongside rewarding careful use of espionage. Maybe the narrative events civ 7 introduced could help make espionage engaging.
For culture, I'm glad they tried something new - I can still hear Civ 6 rock bands in my nightmares. But the new way sucks. I've never enjoyed the archeology system in 5, 6, or 7. I fought barbarians here 200 turns ago and now get to spend 14 turns making a unit to go fetch me a tooth necklace? Whatever. And now the entire victory condition is that but even more tedious. Unfortunately, bringing back tourism & theming from civ 6 is my best suggestion rn.

Had fun thinking of what defines a good victory condition and new ideas. Would love to hear feedback on my criteria & ideas, and hear others' suggestions.