"what is not possible with RS-232?"

Erik has given you the physical-level, hardware reason.

On a topological level, RS232 is purely a point-to-point interface; it does not support a bus structure.

As you talked about a "network" and addressing, I assume you must at least have point-to-multipoint?
Or multipoint-to-multipoint?

Note that RS-485 is sufficient for a bus structure; it is not necessary.
Again, it depends on your particular requirements & constraints.