First, I think the challenge is that the game is not supposed to be a survival game but with no NPCs or melee your survival depends on ammo. And finding ammo should not be a way to try and extend gameplay.
Once the main story line is done, well, all you have left to do is shoot robots. I love the game but I do not want to spend hours of my time just finding ammo which is why I find myself spending less time playing it each day.
Second, any respawn based on time logic I don’t think will ever work regardless as to what you set it to unless you make that timer visible in game. Don’t leave your users guessing how many game hours have passed. They could be judging time spent accurately but I’m sure you realize most are not and will not. And then users just get frustrated and flood the forums. So if you want the logic to be based on game time in any way then you need a timer visible in game. The other advantage here is that it will help rule out any other issues with respawning if users can see the amount of time elapsed.
Lastly, if you take a look at other open world shooter games like Far Cry, Fallout 4, etc. none of them made just finding ammo and health this difficult and those games still have a very active following.
Again, finding ammo shouldn’t equate to extended gameplay and it feels like that is what they are trying to do. If we can easily find ammo and then continually enjoy the game shooting robots why would this even be an issue to the developers? Perhaps it’s not what the developers originally envisioned but listen to your users. True, some seem to be doing okay but most are not and I have yet to read one post from anyone who said they thought the ammo respawn now made their game play better. They’re just muddling through it.