alt Hacker NewsIt's not a lost skill.
Spinning up a binary and replicating actors across two computers that both have a connection string to a server is.. for all intents and purposes: easy.
Where it falls down is when you start to have complex interactions with AI that's serverside, or you have a dynamic world that changes based on player behaviour, or you have cross platform requirements, integrations with companion apps and above all: matchmaking.
If you're a looter-shooter, there's a whole host of complicated interactions too.
A game like Apex Legends could probably distribute their server binary, but if you require online, as in, not just a single match, but an economy- a dynamic matchmaker and a dynamic world (meaning: when you kick a box it stays kicked) and a persistent account (you keep your loot): then that doesn't work well anymore.
The interactions are just too complex to batten down reliably, they'll be exploited, there'll be no fun, or: it just won't be possible for certain features, regardless of safety.
You can see how this looks by trying to use one of the many unofficial versions of Runescape.
This is the whole spirit of the "Stop Killing Games" argument though: you don't need to keep any of that stuff once support drops. It just needs to be "functional", in the most basic possible sense. If there are no players, no economy, no advanced AI, because it was all disconnected, that's considered fine.
The response of "but that isn't any fun!" is totally irrelevant; you can't preserve the initial experience, but you can preserve the basic software itself so that players still have something to mess with.
Programming-wise, this requires a little more emphasis on a modular implementation that needs to be considered from the start. Otherwise, it seems pretty straightforward. Or am I missing something?