I do want to mention that despite what I said above, I think apps are doing a good job at making exploration kinda easier. Been digging wefwef/voyager and looking forward to Boost and Sync to check out.

Also have experienced all of what you describe.

S.T.A.L.K.E.R Anamoly is free and a great single player fps with a great vibe to it. Doesn't quite fit your criteria though as I wouldn't say there is much of a campaign. Very interesting dynamic world and AI system though.

Edit. Highly recommend the GAMMA version. Get installation files @ their discord.

https://discord.gg/stalker-gamma

In Beaver We Trust.