Electronics guy here. There are devices that speak actual RS-232 with e.g. -3 and 15V as logic levels. And there are devices that also say "RS-232" on their port, but expect logic levels of say 0 and 3.3V (or 5V).

When you use one with the other any number of things can happen, including the destruction of the target microcontroller if the circuit is unprotected (most MCUs dislike sufficiently negative voltages on their ports).

Now if we talk about servers or expensive media gear their RS-232 connectors are very likely top notch (and still very much present as you rightly noticed). Cheap devices are more questionable here.