It's fascinating how different people's experience of things can be! I find exactly the opposite: nukes really spice up late-game wars, and make them much less boring by introducing extra risk and uncertainty. It's a much more serious decision to DOW someone if you know they've might have nukes - much knottier to try to evaluate the potential costs and benefits. And you need to put a whole lot more thought into both preparation and also tactics while you advance: how should you spread out your units so that a single nuclear strike can't completely crush you militarily? Where does the enemy have vision, and where else might they hit? I think it also makes for some of the most tense, exciting and memorable end-games. I expect everyone can remember vividly the crazy times when they were so so close to victory before the stomach-turning sight of that horrible orange glow ruined everything, or when an AI was on the verge of a science victory before a judiciously placed warm nuke gave you the couple of turns leg-up you needed to pull it out of the bag. Then there's the fact that uranium is a strategic resource that you might really want and really not have enough of, so what are you going to do about getting some? There's no other resource that's often an issue in that way apart from iron right back in the very early game. Yes, in many ways nukes definitely add a whole lot of depth to the late game, in my opinion.