That would be an improvement over nothing, but closed-source means that the game is still going to die as soon as someone finds a security vulnerability (or even just a gameplay glitch) that can't be feasibly patched.

Imagine an MMO where special text in the chat causes viewers' clients to crash, or a glitch exists to duplicate items or money, or where anybody can crash the server to run arbitrary commands.

I play SubSpace (a MMO spaceship game released in the 90s) to this day. It was shut down soon after release.

The original server binaries were left on the original CDROM by a programmer.

Then PriitK, a creator of Kazaa and then Skype and Joost!, went on to re-create the client due to cheating/hacking, naming it Continuum.

Years later the server is reimplemented as A Small Subspace Server (ASSS), making it a complete fan remake of the original game (sans graphics). This is also when we finally got server side mods, everything before that was client only or a hack.

We even got on Stream Greenlight.

https://store.steampowered.com/app/352700/Subspace_Continuum...