All the grounded rp's (military, vietnam, falklands, and survival to some extent) have pretty much died because they get stale. There is a finite number of possible events, enemies, or it only caters to a niche. I think the same thing has happened to metro and possibly SCP although i have not been on in quite a long time.
I would +1 if the old gang were able to get back and run the server, the OG colonels, leaders, and staff, but that isn't going to happen.
I do not think a serious roleplay fallout rp would gain too much traction as it is niche, and would lend itself to power gaming/ huge imbalances between players. That happened with survival, leading to its full item wipe which lead to its death. A similar thing happened to vietnam but that one was more called for as the system was becoming/became a cancerous mess of factions, groups, and options. Do i agree with wiping the lot and swapping maps, no. However, that was likely one of the easiest ways to remove the dying server.
Stick to what you have right now and only jump on another server if you can really invest time, money, and devs into it. Half assing any of it and on niche gamemodes will land it in the shitter.