Did we play the same New Vegas? If at all, Fallout 3 should be your point here, as no matter what you do, the endgames outcome is always the same while New Vegas has a shitton of permutations and different (faction) endings.
About the folks saying that NPCs will fix Zomboids endgame... I do not believe this at all. It's just another gameplay feature that you can game and at some point it just won't pose a threat anymore.
My problem with the difficutly is that it's very hard to get the right settings... For me it's always either too easy or too hard. In my last game I drastically increased the Z amount, which resulted in me having to kill hordes of zombies *exactly* every 3 ingame days. It was so unfun... it still wasn't impossible hard, just tedious AND I noticed the pattern in Z spawning and how their ai works. It made me realize even more how pointless it all is. And yes, I had a Van in perfect condition and all the other fancy stuff.
In worst case, you can always do roof camping with a bit farming and you're good to go until you get bored or accidentally fall off the roof and break a bone or two.
What I personally want is a better balanced difficulty... independent of your difficulty settings. Give me hordes of zombies for a while and then let it rest some time. Throw a few here and there around my base maybe, but nothing serious. Then at some point give me a truly apocalyptic horde event or something. But again, even that is pointless if you can just roof-camp it out... Makes me think that zombies should have the ability to clutter up on a wall and use each other as stairs to reach higher ground... But then you just have to roof camp on second elevation buildings. Ugh.