If you don't want to get another message system, there is an easy workaround, as this function is not included in RMXP by default.
Make a new 'Call script' command, and put in:
Expand to see the code.
Where ENEMY_ID is the id of the enemy you want to call, and VARIABLE_ID is a variable thats free to change (i'd recommend setting aside a variable just for showing enemy names).
In your 'Show text', call the name through \v[VARIABLE_ID]. It will show a name instead of a number.
It's untested though; I cant access RMXP from where I am, but it should work