This is not an issue you should be experiencing during normal gameplay. It sounds like your game is crashing. It’d be helpful if you provided the crash logs. After experiencing a crash, you can find the logs by doing the following:
Right-click Unturned in your Steam Library
Select Properties… > Local Files > Browse…
Open the Logs folder
Provide the contents of Client.log file (such as attaching the file to an email, or some similar method of dumping/copy-pasting all of file contents)
Return to the Unturned folder
Open the Unity AppData folder
Provide the contents of Player.log file (such as attaching the file to an email, or some similar method of dumping/copy-pasting all of file contents)
The last few years of Unturned’s development have been devoted to fixing the issues you describe. As you said, a skyscraper with a weak foundation is a poorly designed skyscraper. But you should remember that replacing the foundation of a building is very difficult.
I would assume this is due to your PC running out of resources and thus, stop responding. Unturned’s poor memory performance contributes to this.
What do you consider as high RAM usage, and how much does your computer have? I think the only game I’ve had memory issues with was Cities: Skylines, it’d crash from trying to use too much memory. There have been a few cases where I noticed memory leaks coming from Unturned but they never reached the point where it became a problem.
I want to say this is a Windows issue and not Unturned, although with how long the initial load is, I don’t want to say it has absolutely nothing to do with the game. Is it only during certain times? Does it happen with other games too?
I’m going to go with your issues in Unturned being partly due to your computer’s hardware.
I assume Unturned will back off on the memory usage if you’re running near the limit, but it uses 4.5-5 GB when I load into the main menu, and around 7.6 GB after entering/exiting a few maps.
Specifications listed for games normally aren’t that accurate, but the current ones for Unturned list 8 GB as a minimum with a recommendation of 16 GB.
The issue with your CPU is most likely the fact that it is only a dual-core. What does the usage sit at when idling, in Unturned, and in those two games you say you can run fine? Another possibility may be that the CPU is struggling the same in all three, but graphics are causing a slowdown for Unturned.
There definitely is a difference in disk usage, the only thing I can offer there is check if your computer has a hard drive or an SSD.
I played unturned with very similar, if not the same specs a couple years ago. If you will put in-game resolution to 1280x720 60hz and put all your graphics settings at low (100% nearby draw distance and animations on ultra because they dont eat performance) you will have a solid 50-60fps or so on vanilla servers on maps like PEI, Yukon and Washington