There are only 4 successful general purpose production OSes (GNU/Linux, Android/Linux, Windows, OS X/iOS) and only one of those made by the open source community (GNU/Linux).
And a new OS needs to be significantly better than those to overcome the switching costs.
> There are only 4 successful general purpose production OSes
Feel like you are using a very narrow definition of "success" here. Is BSD not successful? It is deployed on 10s of millions of routers/firewalls/etc in addition to being the ancestor of both modern MacOS and PlaystationOS...
> And a new OS needs to be significantly better than those to overcome the switching costs.
Who cares if nobody switches to it as their daily driver? The goal you proposed was "viable", not "widely used". The former is perfectly possible without LLMs (as history has proved), and the latter is unrelated to how you choose to make the OS.